Background: Given that behavior-related risk factors cluster together in individuals and populations it is important to study their patterns to inform Public Health interventions and decisions aimed at controlling disease and promoting health. This study examines the clustering and variation across different socio-demographic groups of four major behavioral risk factors (smoking, heavy drinking, physical inactivity, and unhealthy diet) in two groups of the Portuguese adult population, one with and one without diabetes. Methods: The study sample was derived from the 2005/2006 National Health Interview Survey for Portugal. Clustering was evaluated by comparing the observed and expected frequency of the different possible combinations of the four risk factors. A binary multiple logistic regression model was fitted to examine the socio-demographic variation in the clustering of the four risk factors. Results: Among the Portuguese population (584,286 individuals surveyed), 8.9% of diabetics and 19.5% of non-diabetics accumulated two or three behavioral risk factors. Behavioral risk factors are explored considering all possible multiple combinations (k = 16). The most frequent combination was smoking and unhealthy diet. Conclusions: These findings suggest that the likelihood of individuals having two or more risk behaviors simultaneously was greater in men 35-44 years old and lower education level both in diabetics and non-diabetics.