AIM. To investigate illness perception in patients with type 2 diabetes mellitus and its association with the degree of control over relevant cardiovascular risk factors. METHODS. A cross-sectional questionnaire-based study was performed from June 2007 to March 2008. A stratified random sample of 46 Croatian general practitioners was asked to select, using systematic sampling, the first 6 patients with type 2 diabetes mellitus aged > or =18 years who visited them for consultation during the study period. Data on 250 patients included patient illness perception assessment (Brief Illness Perception Questionnaire, IPQ), cardiovascular risk factors, and socio-demographic data. RESULTS. The patients' mean age was 63.0+/-10.9 years and mean duration of diabetes was 9.3+/-7.8 years. The patients' illness perception assessment on an 11-point (0 to 10) scale showed the highest median scores (interquartile range): 10 (8 to 10) for "timeline" and 8 (7 to 9) for "treatment control," followed by 7 (5 to 8) for "personal control," 7 (5 to 9) for "understanding," 5 (3 to 7) for "consequences," 6 (4 to 7) for "concern," and 5 (2 to 7) for "emotional response." The lowest score was 3 (1 to 5) for "identity." Multivariate logistic regression showed that the Brief IPQ item "concern" (P<0.001) was a significant predictor of body mass index; "personal control" (P<0.001) and "concern" (P=0.048) were significant predictors of fasting blood glucose; "treatment control" (P=0.009) was a significant predictor of total cholesterol; and "understanding" (P=0.010) was a significant predictor of blood pressure. CONCLUSION. As patients' beliefs seem to be associated with the degree of control over cardiovascular risk factors, they should be included in routine clinical assessments.