The impact of laterally non-uniform carrier lifetime on the determination of the lifetime from photoconductance-based measurements, based on the self-consistent method proposed by Trupke and Bardos, is investigated using a simple model. It is shown that the method can result in an overestimation of the mean lifetime, with the magnitude of the error mainly dependent on the distribution of the effective lifetime across the area sensed by the photoconductance coil. Although in many cases the error introduced will be relatively small (in the order of 5% or less), much larger errors can result in some cases, such as for samples that feature small areas with a significantly higher than average lifetime. The error can be eliminated through independent measurement of the sample optical properties. Experimental measurements confirm the model predictions. Copyright © 2012 John Wiley & Sons, Ltd.