BACKGROUND There is disagreement on the effect of diabetes on oral hygiene. The purpose of this study was to assess the oral health and hygiene status of type 1 diabetic patient. METHODS In this case control study, periodontal health and hygiene of 80 children and adolescents (5-18 yr of age) with type 1 diabetes mellitus referred to Pediatric Endocrine Clinic of Besat Hospital Hamadan Iran 2013 - 2014 and 80 non diabetic control subjects were clinically assessed. The required data such as sex, age, duration of the diabetes, type and number of insulin injections per day were obtained from self-administered questionnaire and the patient's medical records. Participants in both groups were examined for Decay-missing- filled teeth (DMFT); dmft (for primary teeth), oral hygiene using O'Leary plaque index (PI) and gingivitis index (GI). P<0.05 was considered significant. RESULTS The mean age of the study and the control group was 12.5±4.05 and 12.08±3.47 yr, respectively. There were no significant difference between two groups in terms of DMFT (P=0.158) and PI indices (P=0.373). The GI index difference was statistically significant in diabetic group (P=0.001). Interestingly, a higher dmft index was observed in the control group (P=0.008). In diabetic groups, GI and DMFT index increased significantly with duration of diabetes. CONCLUSIONS Apart from higher scores of GI index, frequency of oral and periodontal disease was not different in diabetic patients compared with healthy subjects. Findings of present study are insufficient to support a significant effect of diabetes on increasing the risk of oral and periodontal diseases. However, diabetic children and adolescents should receive oral hygiene instruction.