In many measurements used for the determination of optical properties of biological tissues, a detector with a small cone of acceptance is used. Therefore a small part of the anisotropically distributed backscattered light is detected. We present the results of Monte Carlo calculations and study the anisotropy of the direction distribution of volume-backscattered photons. Close to the source it is impossible to give a general correction factor to relate the measurements to theoretical results. Far from the source, the measured radiation divided by the square of the sine of the accepting angle of the detector is a relatively good approximation of the radiant exitance at the surface of the sample under investigation. We recommend the use of a detector with a large angle of acceptance for these kinds of measurements.