In this review, 3D dosimetry is divided in three categories; "true" 3D, semi-3D and virtual 3D. Virtual 3D involves the use of measurement arrays either before or after beam entry in the patient/phantom, whereas semi-3D involves use of measurement arrays in phantoms mimicking the patient. True 3D involves the measurement of dose in a volume mimicking the patient.There are different advantages and limitations of all three categories and of systems within these categories. Choice of measurement method in a given case depends on the aim of the measurement, and examples are given of verification measurements with various aims.