We present a short review of applications of a contactless modulation spectroscopy called photo reflectance (PR) to semiconductor quantum dots investigations. The derivative-like spectra and high sensitivity to optical transitions are the reasons why this method. since half of eighties, has become one of the most useful and widely used experimental technique in the investigation of low-dimensional structures like quantum wells, superlattices and heterojunctions. When quantum dot structures had been manufactured for the first time there appeared some attempts of an application of PR and other modulation techniques in studies of fundamental physical properties of those nanometer scale objects. It turned out that PR can be alternative and even better (giving more details) in comparison to common optical experiments. (C) 2003 Elsevier B.V. All rights reserved.