Background. Studies of the relationship between leisure time physical activity, sedentary behaviour and substance use among adolescents report contradictory results. The aim of our study was to examine the association between self-reported leisure time physical activity, sedentary behaviour and alcohol, tobacco and cannabis use among adolescents in Slovenia. Methods. Subjects consisted of 822 school children aged from 14 to 16 years, living in urban area of Ljubljana and Maribor. The data was collected using the EURO URHIS 2 survey. Logistic regressions were conducted to assess the correlation between the independent variables of physical activity; time spent watching television and using the computer, and each of the five substance use dependent variables. Results. Frequency of daily smoking was significantly associated with leisure time physical activity, while alcohol and cannabis use were not. Watching TV ≥ 2 hours per day was associated with heavy episodic drinking in the past month, no associations were found for smoking and cannabis use. Using the computer ≥ 2 hours per day was positively associated with daily smoking, drinking alcohol in the past month, heavy episodic drinking in the past month and ever being intoxicated, while cannabis use was not. Conclusions. These findings suggest that leisure time physical activity is associated with daily cigarette smoking, and leisure time sedentary behaviour is associated with alcohol and tobacco use among adolescents. The results of our study show the need for the formation of suitable preventive measures concerning reduced sitting time as well as leisure time physical activity targeted to adolescents. Izhodišča. Podatki iz do sedaj znanih študij, ki opisujejo povezavo med telesno aktivnostjo v prostem času, oblikami sedečega vedenja ter uživanjem psihoaktivnih snovi med mladostniki, so si nasprotujoči. Namen študije je bil preučiti povezanost med samoocenjeno telesno aktivnostjo in oblikami sedečega vedenja (uporaba računalnika, gledanje televizije) v prostem času ter uporabo alkohola, tobaka in marihuane med mladostniki v Sloveniji. Metode. Podatki so bili zbrani v okviru presečne pregledne raziskave o zdravju mladostnikov EUROURHIS 2. Sodelovalo je 822 srednješolcev, ki živijo v urbanem okolju Ljubljane in Maribora, starih od 14 do 16 let. Z logistično regresijo smo ocenili korelacijo med neodvisnimi spremenljivkami telesne aktivnosti in časa, porabljenega za gledanje televizije in uporabo računalnika, ter vsako od petih odvisnih spremenljivk uživanja psihoaktivnih snovi. Rezultati. Telesna aktivnost v prostem času je statistično pomembno povezana s pogostostjo dnevnega kajenja, medtem ko povezave z uživanjem alkohola in uporabo marihuane nismo dokazali. Gledanje televizije dve uri ali več na običajen šolski dan je statistično pomembno povezano z občasnim čezmernim pitjem v zadnjem mesecu, povezava s kajenjem tobaka in marihuane ni ugotovljena. Uporaba računalnika dve uri ali več na običajen šolski dan je statistično pomembno povezana z dnevnim kajenjem tobaka, uživanjem alkohola v zadnjem mesecu, občasnim čezmernim pitjem v zadnjem mesecu in opitostjo vsaj enkrat v življenju, povezave z uporabo marihuane nismo dokazali. Zaključek. Med mladostniki je telesna aktivnost v prostem času povezana z dnevnim kajenjem tobaka, oblike sedečega vedenja pa z uživanjem alkohola in kajenjem tobaka. Rezultati raziskave kažejo na potrebo po pripravi ustreznega preventivnega programa, s katerim bi sočasno spodbujali telesno aktivnost in omejevali oblike sedečega vedenja.