The Purpose of the current study was to evaluate radiographically the effect of using OT CAP, OT unilateral and magnet extra-coronal attachments placed on second premolars with different RPD designs on the distal implant placed in mandibular unmodified kennedy class II cases. Materials and methods: Twenty-one patients having unmodified mandibular kennedy class II with distal implant installed in the molar region.  Group I patients were rehabilitated with an implant assisted removable bilateral partial denture retained by ball and socket extra-coronal attachment (OT CAP attachment Rhien 83, Italy). Group II were rehabilitated with an implant assisted removable bilateral partial denture retained by magnet attachment (Dyna system magnet). Group III Patients were rehabilitated with unilateral (side plate) removable partial denture retained by another design of extra-coronal attachment (OT unilateral Rhien 83, Italy). Peri-implant marginal bone loss was evaluated around the distal implant in each group using standardized periapical intra-oral radiographs using a long cone paralleling technique. The peri-implant marginal bone loss was measured at the time of loading of the distal implant (0 month), after 6 months and 12 months. Results: There was no statistically significant difference in the mean marginal bone loss (P> 0.05) between the OT unilateral, magnet and OT CAP attachment groups at 0-6 months follow up interval. There was a statistically significant difference in the mean marginal bone loss around the distal implant between the three groups in the (6-12 months) and (0-12 months) follow up intervals. The highest peri-implant marginal bone loss was recorded in group III with the unilateral partial denture design. Conclusion: Within the limitation of this study it could be concluded that although enrolling extracoronal attachments in the design of Kennedy class II is acceptable as a treatment modality, the unilateral design may cause the highest bone resorption around the distal implant.