The tumor stroma, which accounts for a large part of the tumor mass, represents an attractive target for the delivery of diagnostic and therapeutic compounds. Here, the focus is notably on a subpopulation of stromal cells, known as cancer-associated fibroblasts, which are present in more than 90% of epithelial carcinomas, including pancreatic, colon, and breast cancer. Cancer-associated fibroblasts feature high expression of FAP, which is not detectable in adult normal tissue but is associated with a poor prognosis in cancer patients. The present invention provides small-molecule radiopharmaceutical and imaging agents based on a FAP-specific inhibitor.