Ahonen (2008) and Goggin (2011) expand the systematization of the media and list mobile phones as the seventh medium. High school students who were the subject of this research were born between 2002 and 2006, and according to the Theory of generations (Mannheim, 1952; Strauss and Howe, 1997) they belong to the Generation Z. This generation is strongly coexisting with smartphones and spends much of its time using them. The basic research problem of this doctoral study is based on the fact that Croatian high school students spend a lot of time on their smartphones. The aim of this study is to test, in the context of the Uses and gratification theory, the motives and expected gratification that drive Croatian high school students to use smartphones, as well as to explore their media habits. The mentioned research problem is a frequent subject of research in many scientific fields such as medicine, psychology, biology, sociology, and other sciences. The aim of this paper was to approach this research problem from the discourse of information and communication sciences. At the very beginning of drafting this doctoral study, the question arose how to find a suitable information and communication theoretical paradigm that would, as a recognized scientific model, lead such research to new scientific knowledge and solutions, and direct it to the scientific interpretation of experimental observations (Kuhn, 1970). As the aim of the research was focused on understanding the reasons for media consumption, Uses and Gratification Theory was chosen as a key paradigm. This communication theory is positivist in its approach, based on the sociopsychological communication tradition (Katz, Blumler and Gurevitch, 1973; Severin, 1997). In collecting data for researching media habits and expected gratification of respondents from the use of smartphones, a mixed research approach was used with intertwining of quantitative and qualitative methods (Este, Sitter, and Maclaurin, 2009). Quantitative research was conducted through a questionnaire on a stratified random sample of 1507 Croatian high school students. The research was conducted in 30 Croatian high schools and distributed in all four traditional Croatian regions. The survey was conducted as a quantitative cross-sectional study on a stratified random sample. The stratification of the sample will be conducted based on data on secondary schools from the Release of the Central Bureau of Statistics of 30 April 2020 (Central Bureau of Statistics, 2020). After carefully studying the numerous typologies of gratitude from the use of media and noting their great dispersion, we began to condense the multitude of gratifications/motives into four conceptually broader groups of gratifications/motives, which led to our own typology. Qualitative research was conducted through a focus group in which 6 high school students participated. Prior to the research, a focus group research protocol was developed based on recent scientific literature dealing with the study of Uses and gratification theory in the context of smartphone usage. The focus group discussion was based on eight basic groups of questions with sub-questions that seek to reach new scientific findings and clarify the findings of quantitative research. The findings of the research showed that Croatian high school students spend an average of 5 hours and 26 minutes a day on their smartphones. The most used app on a smartphone is Instagram followed by Snapchat, WhatsApp, YouTube and TikTok. The research showed that students are mostly driven to use smartphones by social motives (M = 4.26, SD = 0.69), then eudemonistic (M = 3.98, SD = 0.65), hedonistic (M = 3.89, SD = 0.85) and finally motives of self-expression (M = 3.32, SD = 0.93). Predictor that most strongly positively predicts the time spent on a smartphone is hedonistic (β = 0.200, p <.001). With each point up the scale of hedonistic motives, participants spend an average of 32.6 minutes more on a smartphone. The difficulty encountered in the research was related to the fact that the motivation of the respondents in using a smartphone changes from second to second because the respondents are multitasking. Multitasking makes it quite difficult to identify and specify the expected pleasures of using smartphones. It blurs the connection between, for example, information and entertainment and users surfing imperceptibly through numerous platforms, media channels and media content, in search of entertainment get information, and vice versa (Martinoli, 2013). All of it leads to an overlap of expected gratification. This doctoral study is expected to contribute to the communication sciences by expanding the application of Uses and gratification theory to the study of the smartphones from the discourse of the media and their users as media audiences. It is estimated that this research will fill the gap in Croatian media research in which the research of Croatian high school students belonging to Generation Z in the context of media audience is poorly represented. The research could have its practical value, through encouraging educational policy makers to strategic interventions in the curricula of cross-curricular topics from 1st to 5th educational cycle, which would direct students from 1st grade to the end of high school, to review their own media behaviours in the use of smartphones as well as the expected gratification that result from it. In future research on the use of smartphones in the context of Uses and gratification theory, one could compare the expected and obtained gratification from their use. This research would be particularly interesting because the difference between what media audiences seek through their patterns of media use and what they actually gain has a strong impact on their media behaviour.