ENRecent modern life, increased automatization of all works and popularization of sedentary lifestyle raises the importance of mental work. At the same time allotted for regular physical activity (PA) decreases. Thus activity has twofold effect on teenager’s health: temporary and long-term health effects. Recently it is seen tendency that more and more schoolchildren are not meeting recommended amount of PA, and it is getting worse and worse. Therefore, this study was designed to establish 14–17 year-old students’ academic achievement, physical activity and physical fitness interrelationships. Material and Methods. The study included 14–17 years old aged 589 pupils: 285 boys and 304 girls. Physical Activity (PA) was measured by modified short form of international PA questionnaire (IPAQ). According to the modified recommendations, all respondents were divided into three activity groups. For assessment of student’s physical fitness Eurofit fitness test battery (2002) was used, and there were assessed these physical fitness components: balance, speed of limb movement, muscle strength and endurance, explosive power, flexibility, agility. Evaluation of all these fitness components according to reference scales and summing best three of them allowed us to get total physical fitness score (FFS). Student’s academic achievements were registered taking data from electronic journals or diaries. Students according to their academic achievement (AA) were split into 5 groups: excellent, very good, good, satisfactory and poor learners group. Results. Comparing students’ academic achievement between different age groups, gender and PA groups were not established statistically significant differences (p>0.05).After analysis of students’ total amount of PA (MET’s/week.) were identified statistically significant differences between genders (boys were more physically active) and different ages (younger students were more active) subjects (p <0.05). Student’s from excellent and good AA groups less time had devoted to vigorous PA (d./week.) and student’s from excellent and poor AA most time allotted to low PA (walking) (min/d.). It was established that only 9.3% of students experiencing the recommended health-related PA – more than 60 min/day. Comparison of students different PA groups physical fitness showed that more physically active students presented better physical fitness results (p<0.05), while excellent AA group students demonstrated better upper limb movement speed (p<0.05). Conclusions. It was established weak correlation between total amount of physical activity and average physical fitness score (FFS) (p<0.05), between the academic achievements and total amount of physical activity as well as average physical fitness score (FFS) statistically significant correlation was not identified (p>0.05). Nevertheless, analysing academic achievements with separate physical fitness components, there was established weak but statistically significant positive correlations with abdominal muscle strength and endurance, flexibility and speed of limb movement (r=0.125 and 0.310, p<0.01). A deeper analysis of the results of academic achievement, physical activity and physical activity revealed weak correlation between the total amount of physical activity and the mean score for the pupils’ formal (r=0.190, p<0.01) and humanitarian (r=0.179, p<0.01) subjects, i.e. better learners in both the formal and the humanitarian ones were more active (it should be noted that the averages of these subjects were very closely related to each other).