Abstract. A portable cosmic muon detector has been developed for geophysical applications: searching for large scale underground rock/soil inhomogeneities and underground cavities. The designed muon telescope called a muon tomograph is based on the recently developed closed cathode chamber (CCC) technology, which provides a cheap, easy handling, portable, and power efficient detector system able to work even in extreme conditions (e.g. high humidity, low/high temperature). The muon telescope has a detection surface of approximately 0.1 m² with a 10 mrad angular resolution. Tests have been performed in natural caves and artificial tunnel systems as well. In this paper a summary of the first results on tomographic cavities are presented and the geophysical and possible industrial use of the cosmic muon tomographic technology is indicated.