Polypyrrole-silica, polyaniline-silica and polypyrrole-tin(IV) oxide colloidal nanocomposites have each been characterized by BET surface area measurements. This technique yields the specific surface areas of the nanocomposites, which are substantially higher than that estimated from our transmission electron microscopy studies, even allowing for the unusual 'raspberry' morphology of these particles. We conclude that these nanocomposite systems have significant porosity. For the polypyrrole-silica nanocomposites, there is a strong correlation between the silica content of these materials and their BET surface area.