An efficient method for accurate species (such as CO) concentration predictions on artificially thickened flames is proposed and demonstrated for the Cambridge swirled flame. This method relies on corrections of the (side-) effects introduced by the (dynamic) flame thickening and wrinkling models, applied as an LES post-processing step. This technique provides better predictions of minor species in the inner reaction zone wherever a thickened flame model is used-provided that the flame burns in the flamelet regime, and that the interest is on inflame data rather than on post-flame data. A demonstration for CO concentrations is given and compared to experimental evidence. It is concluded that the thickening factor correction is universal and can be applied for all species, whereas the efficiency factor correction must be adjusted for each species, and heat loss level separately. Both corrections were found to reduce the grid and code dependencies of the results. As this technique is easy to understand, easy to implement and suitable as a correction for available data, we recommend its use in all applications of thickened flame models.