Doped SrTiO3 thin films, 55 nm thick, were epitaxially grown by Pulsed Laser Deposition with niobium contents ranging from 2 to 5 mol% on SrTiO3 and LaAlO3 substrates. The different templates result in different growth defects, film growth mechanism and therefore a different volume fraction of uniformly strained film under the critical thickness. The investigation of the conductivity reveals a significant difference between the two substrate choices, but only at elevated temperatures with conductivity values up to 30% larger for films on SrTiO3 substrates compared with LaAlO3. Whereas in bulk ceramics the niobium level dictates the total conductivity, here it was found that the substrate choice had a greater influence for thin films, in particular at temperatures over 400 degrees C. This finding provides important information on conductive layers in complex heterostructures where strain and defects could work cooperatively. (C) 2013 Elsevier B.V. All rights reserved.