Ab initio calculations of the electronic and magnetic properties of metallic nanostructures on (001) surfaces of Cu and Ag are presented. The LDA approximation of the density functional theory and the KKR-Green's function method are used. It is shown that 3d, 4d and 5d small clusters can be magnetic on metal surfaces. The effect of intermixing with the substrate on the magnetic properties is investigated for Fe clusters on Cu(001). The influence of the geometry and the size of the clusters on the magnetic properties of 4d clusters is shown. Sizeable magnetic moments for 5d clusters are found on the Ag surface.