The assessment of periodontal lesions based on conventional two-dimensional X-ray images is often limited, especially regarding furcations. Nevertheless, periodontal diagnostics, planning and therapy based on clinical examination and conventional X-rays (panoramic and single tooth X-rays) are sufficient in daily routine in the vast majority of patients. In cases lacking sufficient information or showing an atypical clinical course of treatment, a cone-beam computed tomography (CBCT) scan can be very useful for planning and estimation of the prognosis in cases with deep bony pockets and furcation involvement. In complex cases there is an indication for CBCT scanning in periodontology whereas in routine cases the higher radiation dose is not justified and so CBCT scanning is inappropriate.