It has long-been hypothesized that changes in non-protein-coding genes and the regulatory sequences controlling expression could undergo positive selection. Here we identify 402 putative microRNA (miRNA) target sequences that have been mutated specifically in the human lineage and show that genes containing such deletions are more highly expressed than their mouse orthologs. Our findings indicate that some miRNA target mutations are fixed by positive selection and might have been involved in the evolution of human-specific traits.