Typically, scatterers in an environment are not distributed uniformly but rather observed to occur in clusters. Identification of clusters is an issue under discussion. To this end, we study the effect of number of clusters on channel model through computer simulations. We focus on a geometric stochastic directional channel model based on COST259. Fixing a scatterer scenario, we calculate root mean square delay and angular spreads when scatterers are grouped into varying numbers of clusters and study how sensitive these parameters are to the number of clusters used in this channel model. © 2006 IEEE.