36 patients undergoing total hip arthroplasty were randomized to undergo acetabular component placement using either patient-specific instrumentation (PSI) or standard mechanical guides. The purpose was to evaluate whether the use of PSIs resulted in more accurate positioning of the acetabular cup with respect to preoperative planned angles of anteversion and abduction. CT assessment postoperatively demonstrated more accurate positioning of the acetabular component with respect anteversion, although no significant differences between groups were noted in abduction. Effect of PSI on anteversion was more pronounced when the posterior surgical approach was used as opposed to the direct lateral approach.