A diagnostic device for morpho-functional investigations, comprising: - a base having a receiving area designed to receive a patient; - measuring means mounted on the base for performing a diagnostic investigation of at least a part of the patient positioned in the receiving area, wherein the measuring means comprise at least a first and a second measuring ring (5,6) positioned around the receiving area and designed to perform relative investigations on different parts of the patient, the first measuring ring being of the scintillation type and having an internal diameter (d) less than the internal diameter of the second measuring ring, wherein the base comprises a support structure on which the measuring rings (5,6) are applied; the first measuring ring being located in a position corresponding to a portion of the receiving area designed to receive the head of the patient and the second measuring ring being located in a position corresponding to a portion of the receiving area designed to receive the torso of the patient, wherein the measuring rings (5, 6, 7) are positioned according to respective substantially horizontal planes and wherein the support structure extends in a substantially vertical direction for positioning the first measuring ring above the second measuring ring, and wherein at least one of the measuring rings (5, 6) is designed to perform a PET type investigation and comprises an annular outer case and a succession of scintillation elements included inside the outer case, the succession of scintillation elements being movable laterally by rotating around the receiving area in such a way as to acquire at least two images rotated between each other by a predetermined angle. - a base having a receiving area designed to receive a patient; - measuring means mounted on the base for performing a diagnostic investigation of at least a part of the patient positioned in the receiving area, wherein the measuring means comprise at least a first and a second measuring ring (5,6) positioned around the receiving area and designed to perform relative investigations on different parts of the patient, the first measuring ring being of the scintillation type and having an internal diameter (d) less than the internal diameter of the second measuring ring, wherein the base comprises a support structure on which the measuring rings (5,6) are applied; the first measuring ring being located in a position corresponding to a portion of the receiving area designed to receive the head of the patient and the second measuring ring being located in a position corresponding to a portion of the receiving area designed to receive the torso of the patient, wherein the measuring rings (5, 6, 7) are positioned according to respective substantially horizontal planes and wherein the support structure extends in a substantially vertical direction for positioning the first measuring ring above the second measuring ring, and wherein at least one of the measuring rings (5, 6) is designed to perform a PET type investigation and comprises an annular outer case and a succession of scintillation elements included inside the outer case, the succession of scintillation elements being movable laterally by rotating around the receiving area in such a way as to acquire at least two images rotated between each other by a predetermined angle.