Aim:The primary objective of the study was to examine how adolescents assess their own quality of life, and whether this is related to their level of physical activity and time spent in front of screens. Also, whether these relations change in a period of 3 years, ie between two measurement points (the beginning of high school in 2014 and the end of high school in 2017.). To this end, we have identified three sub-goals. The first was to examine whether there was a change in the time spent in front of the screen, the level of physical activity and assessments of the quality of life of adolescents of different genders and types of school in the period of 3 years (2014-2017). The second objective was to examine the relationship between screen time and physical activity levels with adolescent quality of life assessments at each measurement point (2014 and 2017). The third objective was to examine whether there were differences in the time spent in front of the screen, the level of physical activity and the quality of life with regard to the gender of the participants and the type of school they attended at each measurement point. The research was conducted on a total of 916 participants, 444 students and 459 high school students from the City of Zagreb, and is part of the CRO-PALS study. Methods: quality of life was assessed by the Croatian version of the KIDSCREEN-27 questionnaire. Time spent in front of the screen and physical activity were assessed by the SHAPES questionnaire. Results:adolescents have been shown to be less satisfied with their quality of life in the final grade. Girls are more dissatisfied with school performance and the school environment, health status and amount of physical activity, family relationships and amount of free time, and feel less sad and lonely than boys. The boys' satisfaction with their health condition decreased as well as the amount of physical activity and they had less free time in final grade than in first one. Vocational school students are less satisfied with school success and financial resources. Resaults show visible reduction in time in front of the screen, a high correlation of time in front of the screen with poorer mood, school success and health. More time in front of the screen is spent by boys in general, students of vocational schools, especially girls compared to grammar school girls. Girls are generally less active than boys, and boys from vocational schools are more active than grammar school students. On average, girls were less satisfied with school performance and were less able to attend classes, as were vocational school students compared to high school students. In the first measurement, girls are more dissatisfied with their health, amount of physical activity, emotional state and amount of free time than boys. Vocational school students are less satisfied with their income than high school students.