Abstract Copper clusters grown on a reconstructed TiO 2(1 1 0) surface were studied by scanning tunneling microscopy (STM). The titania surface exhibited low energy diffraction patterns corresponding to the (1×2) reconstruction, but STM studies revealed that this surface was not fully reconstructed. Specifically, gaps in the characteristic (1×2) atomic row structure were observed, illustrating that this partially reconstructed surface is much more defective than the (1×1) surface. Copper clusters grown on the reconstructed TiO 2(1 1 0) surface showed the same basic self-limiting growth characteristics as Cu on TiO 2(1 1 0)-(1×1). For coverages between 0–0.5 ML, a fairly narrow size distribution was observed, and the island densities rather than cluster sizes increased with coverage. Annealing to 700 K resulted in increased cluster sizes, but the narrow size distribution was maintained. The main difference between growth on the (1×1) vs. reconstructed surface was in the cluster sizes, densities and spatial distributions. On the reconstructed surface, the cluster sizes were smaller while cluster densities were much higher (6.2×10 12 vs. 3.0×10 12 at 0.5 ML), and even the annealed Cu clusters displayed no preference for residing at the step edges. These characteristics are attributed to reduced mobility of the Cu atoms on the highly defective, reconstructed surface.