In this work a review about the dispersion of colloidal quantum dots in polymers as method to implement active waveguides is presented. For this purpose several kinds of nanostructures (CdS, CdTe, CdSe and PbS) were embedded in PMMA to fabricate active planar waveguides in the visible and the infrared. The optimal conditions for waveguiding were obtained and the gain and attenuation carefully studied. When more than one kind of nanoparticles is dispersed in the film the structure can propagate more than one color, being it possible to obtain white light with the right proportions of red, green and blue. The losses can be improved if a polymer cladding is deposited on the QD-PMMA film, and if a pattern is defined on the film the photoluminescence of the QDs can be coupled to a 2D structure. QDs were also dispersed in SU-8 to implement 2D active waveguides. Finally, the nanocomposites are deposited on gold films with the intention to couple light and provide gain in the surface plasmon polariton.