OBJECTIVES: The necessity of a second molar region implant for Kennedy Class II classification of unilateral partially edentulous arches remains controversial. This study aims to compare the effects of implant treatment in the first and second molar regions, providing a basis for planning implant treatments for Kennedy Class II dentition. METHODS: This prospective cohort study included 16 patients with implant therapy up to the first molar and 16 patients treated up to the second molar. Bite force, masticatory function, oral health-related quality of life (OHRQoL), and food and nutrient intakes were evaluated as outcomes. RESULTS: While the two groups showed improvements in occlusal force and masticatory function with implant treatment, the increase was significantly greater with implant treatment extending to the second molar. The improvement in OHRQoL was comparable between both groups. Furthermore, the increases in vegetable, dietary fiber, and vitamin K intakes were significantly greater in the implant treatment group extending to the second molar. CONCLUSION: From the perspective of OHRQoL, implant treatment up to the first molar may be sufficient.