Co80Pt20 alloy films from 125 to 1000 nm thick have been grown by electrodeposition on Cu(111) seed layers under constant current. Their structure, morphology, and magnetic properties have been investigated. Growth conditions can be identified for which the resulting Co-Pt films consist of a hexagonal close-packed phase only, with the c axis perpendicular to the substrate. Grain size in the film plane remains almost constant with increasing thickness, X-ray, atomic force microscopy, and magnetic data pointing toward a columnar growth. The films exhibit hard magnetic properties in the out-of-plane direction with coercivity up to 6.1 kOe. (C) 2003 The Electrochemical Society.