CONTEXT: Malnutrition is frequently observed in inpatients with malignant diseases and may contribute to longer hospital stays. OBJECTIVE: To compare the nutritional status, lymphocyte count, hemoglobin values and length of hospital stay of patients with and without malignant diseases. METHODS: This comparative study assessed indicators of nutritional status, namely body mass index, recent weight loss, lymphocyte count, hemoglobin and length of hospital stay, of 928 surgical patients with and without malignant diseases (50.2% females and 49.8% males). The chi-square test was used to compare proportions and the Mann-Whitney test was used to compare continuous measurements between two groups. The significance level was set at 5%. RESULTS: Patients with malignant diseases had longer hospital stays (P<0.0001), furthermore, a higher percentage of patients with malignant diseases had body mass index <18.5 (P<0.0001) and experienced recent weight changes (P<0.0002). Lymphocyte count also differed statistically between the groups (P = 0.0131), which lower levels were identified among patients with malignant diseases. CONCLUSION: The lymphocyte count, hemoglobin values and weight loss are important findings of nutritional depletion in patients with malignant diseases.