OBJECTIVES: The aim of this study was to determine the incidence of malignant diseases in patients with SLE in the Zadar County in a 15-year period (from 2007 to 2022). MATERIALS AND METHODS; The research included 144 patients with SLE treated in the period from 2007 to 2022. and was conducted by searching the electronic database of the Zadar General Hospital. RESULTS: Out of 144 patients with SLE, 126 were female (87.50%) and 18 were male (12.50%). Out of 12 patients with SLE and malignant disease, 2 were men (16.70%) and 10 were women (83.30%). The average age of patients with SLE was 53 years and the average age of patients with SLE and malignant disease was 61 years. A total of 14 malignant tumors were found, as some patients had more than one tumor. The majority of patients (91.70%) suffered from a malignant tumor after the diagnosis of SLE. The most common localizations of malignant tumors were breast, colon, skin and mother. Three patients from the group with malignant diseases died as a result of malignant tumors. CONCLUSION: Malignant disease occurred in 8.83% of patients diagnosed with SLE. The average age of patients with malignant diseases in SLE is slightly higher than in patients without malignant diseases. The most common localizations of malignant tumors were breast, colon, skin and uterus.