Cone-beam computed tomography (CBCT) has an important function in understanding implant operations. CBCT can be used to evaluate the basic condition of implant site before implant operation and decide whether it is suitable for implanting. CBCT also ensures whether the direction of implant and the operation method are satisfactory. CBCT can be used pre-or post-operation as long as the case involves the maxillary sinus. Clinical implant cases using CBCT were introduced to evaluate the maxillary sinus pre-or post-operation.