The present communication describes the endodontic retreatment of a rare four-rooted maxillary second molar. A 25-year-old patient was referred to our dental practice requesting an apicoectomy because of continuous and permanent pain reaction six months after the first endodontic treatment. The sent radiograph demonstrated three filled root canals (one mesial, two distal) and four radiographically superimposing roots (two mesial, two distal). Due to the diagnosed chronic apical periodontitis and based on the visible untreated root canal, we decided to endodontically re-treat the quadrangular tooth against the referred apicoectomy. In the first session, only the previously untreated mesiopalatal root canal was mechanically prepared and filled with a corticosteroid- and tetracycline-containing paste. After two symptom-free weeks, the gutta-percha was removed from the other canals and calcium hydroxide was applied. Another two weeks later, the four root canals, whose orifices were "irregular quadrilateral" shaped on the pulp chamber floor representing Versiani Type A, were obturated. After the verification of this rare anatomy by cone beam computed tomography, the tooth was classified as Christie's radicular type II. One characteristic of this type is parallel running buccal and palatal roots, which caused a radiographic superimposition and probably led to the endodontic mistreatment in the first case.