Cardiac rehabilitation (CR) is the standard procedure in persons after coronary artery bypass grafting (CABG). Its basic aim is to combat coronary heart disease (CHD) risk factors through physical activity and normalization of body mass. Many authors highlight the differences in response to training in CR as dependent on gender, age and occurrence of accompanying disease. The aim of this study is to assess the effectiveness of a three-week early CR in reference to changing body composition parameters in patients over 50 years of age. The study involved a random group of 65 patients (44 men and 21 women) between the ages of 50–76 (average: 62.6 ± 7.2) years with CHD following CABG. Anthropometric and body composition (bioelectrical impedance method) measurements were taken at the commencement of CR and after the training programme. After CR, body mass and body mass index were reduced in men < 65 and ≥ 65 years, and in women <65 years. A reduction % body fat and increase % fat free mass and % total body water was observed only in patients <65. years. Furthermore, in men < 65 years, an increase in % body cell mass was observed. In women ≥ 65 years, no statistically significant changes were observed in body fat indices and body composition features between initial and final study. Patients ≥ 65 years of age following surgery over a period of hospital cardiac rehabilitation do not experience the same significant improvement in body composition parameters associated with risk of CHD as middle-aged adults. Older women post-cardiac surgery are characterized by a higher disability index in relation to tolerance to physical stress in comparison with men of the same age and persons < 65 years of age.