Several genetically defined hereditary colorectal cancer (CRC) syndromes are associated with colonic polyposis including familial adenomatous polyposis (FAP) and MUTYH adenomatous polyposis (MAP). Limited data exists on the clinical characterization and genotypic spectrum of polyposis syndromes among Hispanics. To describe the phenotype and genotype of Puerto Rican Hispanic patients with FAP and MUTYH and compare with other ethnic and racial groups. Probands were identified from the Puerto Rico Familial Colorectal Cancer Registry (PURIFICAR). Recruited individuals completed risk factors, medical, and family history questionnaires and underwent genetic testing for genotype analysis. Frequency analysis, Chi square, Fisher's exact and Wilcoxon rank-sum tests were used for statistical analysis methods. A total of 31 FAP (from 19 families) and 13 MAP (from 13 families) Hispanic patients recruited from the PURIFICAR were evaluated. Among the FAP cases, mean age at diagnosis was 27.6 (range 9-71 years); 67.7 % cases had more than 100 polyps and 41.9 % had upper gastrointestinal polyps. Among the 19 FAP families, there were 77 affected FAP individuals and 26 colorectal cancer cases. Genetic mutations were available for 42.2 % of FAP families; all mutations identified were unique. Surgeries were reported in 31 cases; 14 (45.2 %) prophylactic surgeries and 6 (19.4 %) therapeutic surgeries for management of CRC. Among MAP cases, mean age at diagnosis was 53 (range 34-76 years). Genetic analysis revealed homozygous biallelic mutations (G382D) in 53.8 %, compound heterozygous mutations (G382/Y165C) in 23 %, and non-G382/Y165C monoallelic mutations in 23 %. Familial cancer registries should be promoted as vehicles for detection, education and follow up of families at-risk of acquiring familial cancers. PURIFICAR is the first and only familial cancer registry in Puerto Rico providing these services to families affected with familial cancer syndromes promoting education, testing and surveillance of at-risk family members, and focusing on cancer prevention efforts. The fact that only 40 % of FAP patients had access to genetic testing stresses the need to promote the establishment of policies supporting genetic testing coverage by medical insurance companies in order to provide patients with the highest standard of care to prevent cancer. Furthermore, our results suggest that Hispanics may have uncommon mutations in adenomatous polyposis related genes, which emphasize the need for full gene sequencing to establish genetic diagnosis.