AIM: This study identified the longitudinal associations between leisure-time sedentary behaviours [television (TV) viewing, computer use and reading (h/week)] and cardiometabolic risk factors, including the metabolic syndrome. METHODS: A total of 2517 participants (mean±SD age: 55.5±4.9 years) were assessed in 2001 and in 2007 for physical activity and leisure-time sedentary behaviours, anthropometry, body composition, blood pressure, fasting blood glucose and lipids, using standardized methods. Multivariate generalized linear (beta, 95% CI and P values) and logistic (OR and 95% CI) regression models were used to assess cross-sectional associations between sedentary behaviours and cardiometabolic risk factors, while a 6-year longitudinal study explored these associations as well as the odds of developing the metabolic syndrome, as defined by the NCEP ATPIII. RESULTS: Increased TV viewing time over the follow-up period was positively associated with increases in body mass index (BMI; P\textless0.01) and percent body fat (P\textless0.001), and marginally with waist circumference (P=0.06). Reverse associations were also found, with changes in BMI, percent fat mass and waist circumference positively associated with TV viewing and computer use. Associations between reading and cardiometabolic risk factors were less consistent. Each 1-h/week increase in baseline TV viewing and in reading was associated with an increase in the chances of developing the metabolic syndrome (OR=1.031, 95% CI: 0.998-1.060, P=0.07; and OR=1.032, 95% CI: 1.002-1.065, P=0.02; respectively). CONCLUSION: The present study data emphasizes the notion of differential associations of specific sedentary behaviours with cardiometabolic risk factors. They are also evidence that different longitudinal associations should be taken into account when designing public health objectives of interventions aimed at improving cardiometabolic health.