Anodic alumina with surface of hexagonal patterned nanodots was prepared by a two-step anodizing procedure. Scanning electron microscope and atomic force microscopy results clearly showed the formation of self-organized hexagonal patterned nanostructure. Diameters of the nanodots were controlled by choosing different anodization voltage and types of electrolyte acids. Co/Pt multilayers deposited on the nanodots with different diameters of 20, 70, and 100 nm lead to the formation of magnetic nanostructures with perpendicular anisotropy. Magnetometry and the first-order reversal curve method were used to study the magnetic properties of Co/Pt nanostructures. An out-of-plane magnetic easy axis was observed for the continuous films and the nanodots with diameters of 100 and 70 nm. The magnetic multilayers deposited on 20 nm nanodots appeared to have taken on a hard axis type behavior. The curvature of nanodot arrays induces strong modifications on the magnetic properties of the nanostructures.