The task of physicians is to provide comprehensive care of their patients. It is necessary not only to treat chronic diseases, but also to reduce the load caused by coexisting risk factors of development of additional diseases and premature death. Nutritional disorders are one of them. Malnutrition are dominant in chronic respiratory diseases, but in certain cases, obesity is also observed. This applies especially to patients with obstructive sleep apnea syndrome (OSAS). Some phenotypes of COPD (blue bloaters) are characterized by obesity. Relationship was also found between obesity and asthma in children, particularly strong in boys. Therefore, for patients with chronic respiratory diseases it is necessary to assess their nutrition status. At the same time obese people should consider the need for diagnostics of OSAS. The diagnosis of obesity involves also simple measurements such as BMI and waist or neck circumference, which should be routinely performed in each patient. The diagnosis of overweight or obesity imposes obligation to undertake holistic treatment based on a diet, change of abnormal eating habits, regular physical activity, psychological support, and in particularly severe cases, pharmacotherapy and bariatric surgery.