This crossectional questionnaire study examined the associations of health factors and psychosocial factors with Health Related Quality of Life (HRQOL) in a sample of adult type I diabetic patients (n = 385). Health related quality of life was measured by the Finnish version of MOS SF-20. Psychosocial measures were general social support, diabetes-specific social support, diabetes locus of control (DCL), self-efficacy, diabetes health beliefs and self-care practices. In multivariate analyses, limitations in physical functioning showed strong associations with perceived health (beta = -0.33, P < 0.001), role functioning (OR = 38.54, 95% CL 10.73-139.56), social functioning (OR = 7.05, 95% CL 2.88-17.27) and pain (OR = 7.89, 95% CL 4.26-14.47), and was moderately associated to mental health (beta = -0.12, P < .01). Duration of diabetes and glycemic control were not related to HRQOL dimensions. Adequacy of social support was related to all HRQOL domains apart from pain and role functioning. The most important diabetes-related psychosocial factors were self-efficacy, and diabetes-related social support. Diabetes-specific factors were more important among those in good physical condition.