The article deals with data treatment problems associated with the estimation (via dual-detection size exclusion chromatography) of the independent distributions of molecular weight and functionality in a derivatized hydroxyl-terminated polybutadiene. Calculations are based on an approach originally developed for linear copolymers and include corrections for (a) effect of functional groups on instantaneous mass and molecular weights, (b) dependence of refractive index with molecular weight, and (c) instrumental broadening. Compared to other more laborious analytical methods, the proposed technique is simple and provides accurate results.