Aim: Obesity is a well-known risk factor in the cardiovascular disease continuum. However, its clinical effects are multimodal, perplexed and non-unanimously understood. Our aim was to assess the prevalence and effects of obesity on the cardiometabolic risk factors and systolic function of left ventricle ejection fraction (LVEF) in patients scheduled for cardiovascular rehabilitation. Methods: A cohort of 302 consecutive patients recently treated for ischaemic or valvular heart disease was matched according to the existence of obesity, defined with body mass index (BMI ≥ 30 kg/m2; n = 90 vs. 212), and the advanced grade of obesity (BMI ≥ 35 kg/m2; n = 19 vs. 283). Nutritional risk screening was performed using the standardised NRS-2002 tool. Results: The mean age of patients was 62.4 11.2 (range 23–86) years; there were more men than women 244 (80.8%) : 58 (19.2%). Group of obese conveyed higher prevalence of ischaemic heart disease than non-obese (OR = 2.69; 95% CI: 1.01–7.20; p = 0.048); while the difference was insignificant for the advanced grade of obesity (n = 17; 89.5%) vs. controls (n = 233; 82.3%; p > 0.05). There was no significant difference in prevalence of other comorbidities (diabetes, glucose intolerance, hypercholesterolaemia, chronic renal and chronic obstructive pulmonary disease) between studied groups (p > 0.05). Utilisation of lipid-lowering drugs was of similar range between the studied groups (p > 0.05), respectively. LVEF (%) was 50.5 8.2 vs. 50.7 7.7 (p > 0.05) and 50.6 7.8 vs. 49.6 10.9 (p > 0.05; Rho = 0.001; p > 0.05), respectively. Conclusion: In studied set of patients, BMI positively correlated with left ventricle dimension and thickness. No significant connection of obesity was found with the prevalence of chronic comorbidities, increased nutritional risk, laboratory diagnostics or systolic function of left ventricle. Existence of obesity paradox in clinical practice was in part reaffirmed with our study.