The aim of this study was to estimate the correlation between the function parameters of the respiratory system and the amount of physical activity, body mass index and aerobic and physical fitness in Daugavpils University students. The study involved a group of 191 students of both sexes from Daugavpils University aged 20–36 years. Students (n = 191, 123 females and 68 males, mean age 24.02 ± 0.24 years) underwent measurement of anthropometric values (height, weight), physical (PWC170 index) and aerobic fitness (predicted VO2max), spirometry (tidal volume, breathing frequency (BF), minute ventilation (MV), expiratory reserve volume (ERV) and vital capacity (VC) and filled in International Physical Activity Questionnaire (IPAQ). Both MV and VC were directly and statistically significantly associated with aerobic fitness, physical fitness and amount of physical activity. Vigorous PA independently was directly and statistically significantly associated with physical fitness and aerobic fitness. After adjusting for sex, BF was inversely and statistically significantly associated with physical activity amount in female. Both female and male had inverse and statistically significant association of BMI and relative VO2max. Reduced lung volumes were associated with lower aerobic fitness, lower physical fitness and lower amount of weekly physical activity. Healthier body mass index was associated with higher aerobic fitness (relative VO2max) in both female and male.