For successful business planning it is essential for a company to quantify its products’ future sales volumes. In this article we present first results on forecasting the diffusion of products in the telecommunication market. The method used is applicable to established products with sales histories as well as to new products prior to their launch. Building on a System Dynamics formulation of the Bass model, Thomas’s framework for forecasting by analogies, i.e. existing products with a high degree of similarity to an innovation, is extended. We illustrate the applicability of the forecasting method by simulating future sales of mobile communication devices and inflight mobile phone usage.