AIM OF STUDY To compare the prevalence of risk factors and severity of atherosclerosis in patients (pts) aged 40 or younger undergoing coronary artery bypass grafting (CABG) in comparison to older pts. MATERIAL AND METHODS Retrospective study involved consecutive 2282 pts, who underwent isolated CABG between 1997 and 2003. Pts were divided into three groups: group A--pts aged 40 years or younger (n=39), group B--aged 41 to 65 (n=1497) and group C--aged over 65 years (n=746). All pts were analyzed for prevalence of atherosclerosis risk factors and severity of atherosclerosis. RESULTS Pts in group A had a higher incidence of active smoking (38.5 vs 18.1 vs 13.0%, for group A, B and C respectively; p < 0.001), hypercholesterolemia (92.3 vs 72.1 vs 66.2%; p < 0.05), positive family history of coronary artery disease (51.3 vs 25.1 vs 8.3%; p < 0.001) and obesity (38.5 vs 32.5 vs 22.8%; p < 0.05). Pts in group A were qualified for surgery more often with single-vessel disease (20.5 vs 2.9 vs 4.2%; p < 0.001). In the spite of this fact, significant impairment of left ventricular systolic performance was noted more frequent in group A (ejection fraction below 40%) (35.9 vs 17.4 vs 13.8%, in group A, B and C respectively; p < 0.05). CONCLUSIONS Compared with the older populations, pts aged 40 or younger undergoing CABG had a higher incidence of active smoking, hypercholesterolemia, positive family history of CAD and obesity. Although atherosclerosis of the coronary arteries is less prominent in young pts, more often it is accompanied by markedly impaired left ventricular function.