We examine the influence of background lumiphore on image quality in luminescence optical tomography. A modification of a previously described algorithm is developed that estimates the background luminescence directly from the detector readings. Numerical simulations were performed to calculate the diffusion–regime limiting form of forward–problem solutions for a specific test medium. Image reconstructions were performed with and without white noise added to the detector readings, using both the original and the improved versions of the algorithm. The results indicate that the original version produces unsatisfactory reconstructions when background lumiphore is present, while the improved algorithm yields qualitatively better images, especially for small target–to–background lumiphore ratios.