In and out of tube: Robust poly-3,4-ethylene-dioxythiophene nanostructures in the form of nanopore arrays and inverse nanotube arrays are obtained by site-selective deposition into TiO(2) nanotubes. The deposition process critically depends on the applied potential and is in line with three-dimensional (3D) progressive and 3D instantaneous nucleation-growth mechanism, leading to the construction of polymer blocks or polymer/semiconductor hybrids.