BACKGROUND: In an online survey of Lithuanian adults (n = 1140) aged 18 to 64 years, we sought to better understand the factors influencing the structure of physical activity (PA). We hypothesised that the PA paradox (i.e. the benefits of PA will be much greater during leisure-time than work-related or household moderate to vigorous PA) occurs more subjectively for psychological well-being indicators, than physiological well-being indicators, and should not depend on age or gender. METHODS: An online questionnaire was distributed as to potential participants through the Facebook social networking website within the period May 2021 to December 2021. PA was assessed using the long version of the International Physical Activity Questionnaire (IPAQ). Mood responses were assessed using the Brunel Mood Scale (BRUMS-LTU). Emotional intelligence was assessed using the Schutte Self-Report Emotional Intelligence Test (SSREIT). Perceived stress was assessed using the 10-item Perceived Stress Scale (PSS-10). Descriptive analysis, a two-way analysis of variance, and linear regression analysis were used to interpret the data. RESULTS: The results revealed that a PA paradox occurred in women and men in terms of health, happiness, vigour and perceived stress, and only in women according to morbidity and overeating. According to the regression analysis, women's and men's subjective health (β = 0.135; p < 0.001), happiness (β = 0.084; p = 0.018) and vigour (β = 0.169; p < 0.001) were significantly positively, and perceived stress (β = -0.088; p = 0.009) negatively correlated (regardless of age) only with leisure-time moderate to vigorous PA. 'Healthy', i.e. the amount of leisure-time PA in men decreases with age, while it does not change in women. CONCLUSIONS: We believe that this study has expanded a clearer understanding of the PA paradox and its possible application to improving the health of individuals of different age groups.