This article examines sedentary behaviours (television viewing, computer use and reading) in relation to obesity among Canadian adults aged 20 to 64 years.The analysis is based on 42,612 respondents from the 2007 Canadian Community Health Survey Cross-tabulations were used to compare the prevalence of obesity by time engaged in sedentary behaviours. Multiple logistic regression models were used to determine if associations between sedentary behaviours and obesity were independent of the effects of sociodemographic variables, leisure-time physical activity and diet.Approximately one-quarter of men (25%) and women (24%) who reported watching television 21 or more hours per week were classified as obese. The prevalence of obesity was substantially lower for those who averaged 5 or fewer hours of television per week (14% of men and 11% of women). When examined in multivariate models controlling for leisure-time physical activity and diet, the associations between time spent watching television and obesity persisted for both sexes. Frequent computer users (11 or more hours per week) of both sexes had increased odds of obesity, compared with those who used computers for 5 or fewer hours per week. Time spent reading was not related to obesity.