OBJECTIVES: This study aimed to compare the oral health related quality of life (OHRQoL) of patients using conventional dentures versus implant-supported overdentures. MATERIALS AND METHODS: This study evaluated the OHRQoL of 90 patients between 35 to 75 years who were selected from several public and private dental clinics in Tehran in 2018. Of all, 45 had conventional dentures of both jaws, and 45 had a mandibular overdenture supported by two implants at the site of mandibular canine teeth and a conventional maxillary denture. The OHRQoL of patients was determined using the Oral Health Impact Prfile-20 (OHIP-20). The questionnaire was translated to Persian, and its content validity and internal consistency were confirmed. Data were analyzed by one-way ANOVA, Mann-Whitney test, and independent t-test. RESULTS: In the conventional denture group, 46.7% had good, 46.7% had moderate, and 6.6% had poor OHRQoL. These values were 55.6%, 37.8% and 6.6% in the overdenture group, respectively. Level of education had a significant correlation with the total score of OHIP-20 in both groups (P<0.05). But no significant association was noted between the residential status and gender of patients with different domains of OHRQoL (P>0.05) except for the psychological disability domain, which had a higher mean value in males with conventional dentures (P<0.05). CONCLUSION: Patients with a mandibular overdenture supported by two implants at the site of canine teeth and a conventional maxillary denture had higher OHRQoL than patients with conventional dentures of both jaws.