Background Femoroacetabular impingement (FAI) describes a painful, abnormal (bony) contact between the femoral neck and acetabulum, which, if left untreated, contributes to early osteoarthritis (OA) of the hip. Despite its flat learning curve and long operation times, hip arthroscopy has been used increasingly often in recent years in the surgery of femoroace-tabular impingement. The mini-open technique ( MOT) offers a possible alternative that addresses the abnormal morphological prominence and allows minimally invasive clearance of hip motion. There is still a lack of information on the influence of the greater degree of soft tissue intrusion inherent to the mini-open approach. Therefore we decided to evaluate the medium-term outcome of the mini-open technique and to compare the results to those of the arthroscopic technique reported in the literature. Patients, Material und Methods 99 patients (105 hips, 40 women, 59 men) underwent mini-open surgical treatment for FAI between 2005 and 2012 and were followed-up for an average of 40.5 months. The evaluation focused on the pre- and postoperative pain intensity (NRS: numeric rating scale), the clinical and functional outcomes such as ROM (range of motion), HOS (Hip Outcome Score) and mHHS (modified Harris Hip Score), changes in athletic behaviour and the satisfaction of the patients. Radiological analysis (a-angle, anterior head-neck- offset (HNO), head-neck- offset ratio, ossification, grade of OA) was performed using preoperative, immediate postoperative as well as follow-up radiographs. Finally our results were compared to those reported for the arthroscopic technique in the literature. Results The average pain level decreased from 6.5 +/- 2.3 to 2.3 +/- 2.6 (p < 0.001). 80% (84) confirmed amean postoperative pain-free period of 29.5 months (2-103 months), and 52.4% (55) were still almost pain-free by the time of the final followup. The mHHS increased from 68.2 +/- 13.5 to 85.2 +/- 18.2 (p= 2 seemto experience insufficient gains from MO surgery, so surgeons should be reluctant to apply the technique under these circumstances.