Abstract: Optical coherence tomograph (OCT) probe device (1) comprising an endoscope (6) which is adapted to be coupled to a light source (2) and has a distal tip portion (6.2), the tip portion (6.2) including focussing lens means (11) and a window (5) for directing light to a subject (7) to be scanned, and for receiving light scattered at the subject (7), to send the scattered light back through the endoscope (6) so that it may be applied to a detector (3) together with reference light, said OCT probe device (1) comprising a beam splitter (13; 17) to separate said reference light from the remaining light, as well as a reference light reflector (4; 20) for reflecting the reference light back so that it is composed to the light returned from the subject (7); the beam splitter (13; 17) and the reference light reflector (4; 20) are located in the tip portion (6.2) of the endoscope means (6) behind the focussing lens means (11) through which the composed light is sent back.