||AIMS/HYPOTHESIS: We examined the association between sitting time and diabetes incidence, overall and by strata of leisure-time physical activity and BMI. METHODS: We followed 28,051 adult participants of the Nord-Trondelag Health Study (the HUNT Study), a population-based study, for diabetes incidence from 1995-1997 to 2006-2008 and estimated HRs of any diabetes by categories of self-reported total daily sitting time at baseline. RESULTS: Of 28,051 participants, 1253 (4.5%) developed diabetes during 11 years of follow-up. Overall, sitting >/=8 h/day was associated with a 17% (95% CI 2, 34) higher risk of developing diabetes compared with sitting </=4 h/day, adjusted for age, sex and education. However, the association was attenuated to a non-significant 9% (95% CI -5, 26) increase in risk after adjustment for leisure-time physical activity and BMI. The association between sitting time and diabetes risk differed by leisure-time physical activity (p Interaction = 0.01). Among participants with low leisure-time physical activity (</=2 h light activity per week and no vigorous activity), sitting 5-7 h/day and >/=8 h/day were associated with a 26% (95% CI 2, 57) and 30% (95% CI 5, 61) higher risk of diabetes, respectively, compared with sitting </=4 h/day. There was no corresponding association among participants with high leisure-time physical activity (>/=3 h light activity or >0 h vigorous activity per week). There was no statistical evidence that the association between sitting time and diabetes risk differed by obesity (p Interaction = 0.65). CONCLUSIONS/INTERPRETATION: Our findings suggest that total sitting time has little association with diabetes risk in the population as a whole, but prolonged sitting may contribute to an increased diabetes risk among physically inactive people.