The diagnosis of malnutrition should be one of the pillars of comprehensive patient care, especially in the case of patients with large wounds, prolonged healing, or comorbidities. The condition for a reliable and accurate nutritional diagnosis is to link it with the parameters of nutritional status assessment at the basic level (anthropometric measurements and clinical assessment) and in depth (biochemical tests and bioelectrical impedance). A prospective study included a sample of 60 patients with coexisting chronic wounds (venous ulcers, diabetic foot syndrome, pressure injury) treated at the Wound Treatment Clinic of Fr. B. Markiewicz Podkarpackie Oncology Center (Poland). The method of estimation and diagnostic survey was used; the research tool was a scientific research protocol consisting of four parts. Self-care capacity was assessed based on the Barthel scale, nutritional status using blood biochemical parameters, and electrical bioimpedance. Wounds were classified according to the extent, depth of tissue structures, and potential infection. Subjects with pressure ulcers had statistically significantly lower fat-free mass component indices compared to those with diabetic foot syndrome and venous ulceration. The subjects with pressure ulcers had significantly lower values of body composition components compared to those with diabetic foot syndrome and venous ulcers. In the group of patients with pressure ulcers, the lowest values of albumin (3.20 g/dL), hemoglobin (10.81 g/dL), and nutritional risk index (NRI) (88.13 pts.) scores were confirmed. Subjects with pressure ulcers with limited self-care presented a non-physiological nutritional status, indicating a risk of malnutrition. Local actions related to wound treatment should be preceded by a general examination, considering the state of augmented nutrition with the use of electrical bioimpedance.