A dental computer tomography apparatus, which includes - an arm structure connected to a body part 10 of the apparatus 1 or to a fixed structure not belonging to the actual apparatus 1, - which arm structure includes an arm part 13 comprising imaging means 14, 15 and which is turnable around a centre of rotation 23, - which said imaging means comprise a radiation source 14 and an imaging detector 15, which are located essentially at the opposite ends of said arm part 13, - a collimator structure for limiting radiation produced by the said radiation source 14 to a beam, - patient support means 16 in connection with an imaging station arranged in connection with the apparatus, and - a control system which includes control means and actuators for controlling and realizing operation and movements of said radiation source 13 and imaging detector 14, as well as for controlling and realizing movements of said arm structure, characterized in that said imaging station is arranged as stationary and said patient support means 16 to position a patient as immovable on a horizontal plane with respect to the imaging station, and in that said arm part 13 comprising the imaging means 14, 15 is connected to said body part 10 of the apparatus, or to some other structure of the apparatus which is fixed with respect to the patient support means 16, via at least two other turnable arm parts 11, 12, which each of the at least two arm parts 11, 12 is arranged to be turnable with respect to at least two centres of rotation 21, 22, 23 locating at a distance from each other and substantially on the same plane, out of which centres of rotation 21, 22, 23, first, the outmost centre of rotation 23 of one of the outmost arm parts 11, 12 connects to said arm part 13 comprising imaging means 14, 15 and, second, the outmost centre of rotation 21 of the other of the outmost arm parts 11, 12 connects to said body part 10 or other structure which is fixed with respect to the patient support means 16. - an arm structure connected to a body part 10 of the apparatus 1 or to a fixed structure not belonging to the actual apparatus 1, - which arm structure includes an arm part 13 comprising imaging means 14, 15 and which is turnable around a centre of rotation 23, - which said imaging means comprise a radiation source 14 and an imaging detector 15, which are located essentially at the opposite ends of said arm part 13, - a collimator structure for limiting radiation produced by the said radiation source 14 to a beam, - patient support means 16 in connection with an imaging station arranged in connection with the apparatus, and - a control system which includes control means and actuators for controlling and realizing operation and movements of said radiation source 13 and imaging detector 14, as well as for controlling and realizing movements of said arm structure, characterized in that said imaging station is arranged as stationary and said patient support means 16 to position a patient as immovable on a horizontal plane with respect to the imaging station, and in that said arm part 13 comprising the imaging means 14, 15 is connected to said body part 10 of the apparatus, or to some other structure of the apparatus which is fixed with respect to the patient support means 16, via at least two other turnable arm parts 11, 12, which each of the at least two arm parts 11, 12 is arranged to be turnable with respect to at least two centres of rotation 21, 22, 23 locating at a distance from each other and substantially on the same plane, out of which centres of rotation 21, 22, 23, first, the outmost centre of rotation 23 of one of the outmost arm parts 11, 12 connects to said arm part 13 comprising imaging means 14, 15 and, second, the outmost centre of rotation 21 of the other of the outmost arm parts 11, 12 connects to said body part 10 or other structure which is fixed with respect to the patient support means 16.