We review the recent progress in the quantitative understanding of light absorption by colloidal semiconductor quantum dots within the framework of the Maxwell-Garnett (MG) effective medium theory. The fundamental quantities used to describe light absorption by dispersed absorbers—intrinsic absorption coefficient, molar absorption coefficient and absorption cross section—are introduced and it is shown that the MG model reduces to a local field correction in the case of strongly diluted dispersions. The correspondence between experimental results and this so-called local field approximation is first demonstrated using PbSe and PbS quantum dots as model systems and then extended to other materials. Moreover, it is shown that by adapting the local field corrections, the analysis can be extended to quantum rods and core/shell heterostructures. Finally, recent applications of these results are discussed and future research directions are indicated.