Background <p>Cardiorespiratory fitness (CRF), assessed by maximal oxygen uptake (VO₂max), is one of the strongest indicators of cardiovascular health and overall risk of death. Somatotype provides a comprehensive description of the morphological constitution of the body, but is seldom used in the context of health or chronic disease risk assessment. The present study aimed to assess the relationship between CRF and somatotype in healthy adult Polish men and women.</p> Materials and methods <p>The study included 276 subjects (146 men and 130 women) aged 18–72 years. Anthropometric measurements were performed using the Martin and Saller method, and the somatotype was determined using the Heath-Carter modification of Sheldon’s typology. The three main components of body composition assessed were endomorphy, mesomorphy, and ectomorphy. In addition, aerobic capacity was estimated using the Astrand-Ryhming test, with blood pressure and heart rate monitored at rest, and the latter also recorded during exercise. Statistical analyses were performed using the Kruskal-Wallis test, Mann-Whitney test and Pearson’s correlation.</p> Results <p>The mesomorphic somatotype was the most common among men, while the endomorphic somatotype predominated among women. Somatotype differentiated body mass index (BMI, kg/m²), waist circumference, and waist-to-hip ratio (WHR), with ectomorphic subjects having the lowest values for these parameters. The highest systolic and diastolic blood pressure measures were found in endomorphic subjects, especially in the female group (respectively, H = 9.3, <i>p</i> = 0.009 and 9.0, <i>p</i> = 0.011). In men, the results of the Astrand-Ryhming test showed that mesomorphs had the highest VO₂max (ml/kg/min and l/min), and ectomorphs the lowest (H = 7.6, <i>p</i> = 0.022 and H = 10.1, <i>p</i> = 0.006, respectively for both units). In women, differences in VO₂max between somatotypes were smaller, though still present. Negative correlations were observed between VO₂max, expressed in ml/kg/min, and the endomorphic component, while positive correlations were observed between VO₂max (l/min) and mesomorphy.</p> Conclusions <p>Somatotype significantly differentiates anthropometric parameters and CRF in adults. Mesomorphy favours higher aerobic capacity, while endomorphy is associated with less favourable blood pressure values and lower VO₂max. These findings highlight the potential value of somatotype as a complementary tool for assessing health risk and planning individual health-promoting interventions. The use of somatotype may be particularly useful given the known limitations of BMI, which does not differentiate between muscle and fat mass.</p>