The most important objective of root canal treatment is to identify all the canals , thorough debridement and three dimenstional obturation of the canal space. The awareness of the anatomy within the canal apparatus is an important component in the treatment of dental procedures. Anatomically mandibular first molars have two roots with either three or four canals, nevertheless, the presence of extra canals has been reported by various authors, most commonly being the middle mesial root canal. The present case illustrates the application of CBCT in the diagnosis and treatment of mandibular first molar with seven root canals. A dental operating microscope was used clinically to detect the seven canals and substantiated using a CBCT scan. In conclusion, the presence of extra canals and the possibility of atypical morphology should be taken into reflection by the clinician during endodontic procedures. Therefore the operator must make an appropriate diagnosis regarding the presence of additional canals for the long-term success of the endodontic procedure.