Effort prediction remains to be one of the greatest challenges of software management. While advances in functional size measurement enable functional size to be successfully utilized for effort prediction there are various factors that create significant variances. One of these factors is functional similarity. In this study, we developed, automated and validated an approach to determine similarities among functional processes for COSMIC functional size measurement methodology. The paper includes the explanation of this new approach and the results of the case study that has been performed to validate the approach.