Wintering roosts of Great Cormorants (Phalacrocorax carbo) on Lake Como, northern Italy, are often inaccessible. We describe an easy-to-build, cheap and efficient technique to collect pellets at inaccessible roosts, which enabled us to study the diet of cormorants without causing disturbance, or killing birds. A floating platform was built using iron bars, sea-plywood panels and plastic tanks which was placed on the lake’s surface, to collect pellets ejected by cormorants using a roost on the eastern shore of the western basin of Lake Como. During two winter periods (February 2001-March 2001 and December 2001-March 2002) 106 samples were retrieved from the platform, measuring 17.5 m².