Purpose: This study was conducted to evaluate bone height around ball and socket and equator attachment in mandibular overdenture retained by single implant. Material and methods: Ten completely edentulous patients were selected with ages ranging from 50-60 years. Single implant was inserted for each patient and they all received heat cured acrylic dentures. The ten patients were divided into two groups, group (I) have received ball &socket attachment, group (II) received equator attachment. In the fitting surface of the lower denture two holes where made between 6 and 7 acrylic teeth and were filled with radioopaque material (amalgam). These represented posterior marker areas of evaluation the bone height. Evaluation of bone height around the implant and the posterior edentulous area which were marked for measurement was done by CAD_CAM CT at the time of attachment placement then after 3 months then 6 months. Results: In our study the comparison of equator and ball and socket attachments regarding the bone height changes around the implant revealed a significant difference. On the other hand there was an insignificant difference when comparing the distal extension area between them throughout the six months studies period. Conclusion: According to this study the equator attachment group indicates lesser marginal bone loss, as compared with the ball and socket attachment group, and there is no difference in bone resorption on the posterior area of the ridge between the two attachments.