Introduction. Diabetes is associated with a lower quality of life (QoL). Insulin therapy is perceived as an additional factor affecting QoL. The objective of this study, using standardized tools, was to evaluate to what extent insulin treatment has an effect on QoL in diabetes. Materials and method. 60 diabetic patients treated with insulin and 90 with oral drugs, all aged over 30, were included into the study. To assess the QoL of patients, SF-36 v.2 and WHOQOL-BREF questionnaires were used. In addition, demographic data were collected. Results. Insulin treated patients had a significantly lower Mental Component Score in SF-36 v.2 questionnaire. No significant differences between the two groups were found in the components of physical domain of SF-36 v.2 and in four domains of WHOQOL-BREF questionnaires. Insulin therapy was significantly associated with lower educational level. The strongest association with QoL in both questionnaires was found for professional activity and age. Conclusions. The results of this study indicate the need for psychological support for patients with diabetes treated with insulin to improve their mental coping. Diabetic patients should also be advised to continue their professional activity for as long as possible due to its important role in maintaining QoL.