The knowledge acquired during university education about organ donation and transplantation (ODT) decisively influences the information future health professionals transmit. This is important in ODT where the participation of the general public is essential to obtain organs. OBJECTIVE: To determine notions of Spanish Medicine and Nursing students on ODT, and the relation with attitude toward ODT. METHODS AND DESIGN: A sociological, multicentre, and observational study. Population: medical and nursing students in Spanish universities. Database: Collaborative International Donor Project, stratified by geographic area and academic course. A validated questionnaire (PCID-DTO-RIOS) was self-administered and completed anonymously. Sample: 9598 medical and 10566 nursing students (99% confidence; precision of ±1%), stratified by geographical area and year of study.RESULTS: Completion rate: 90%. Only 20% (n=3640) of students thought their notions on ODT were good; 41% (n=7531) thought their knowledge was normal; 36% (n=6550) said it was scarce. Comparing groups: there were differences between those who believed that their notions on ODT were good (44% nursing vs.56% medical students;p<0.000), and those who believed it scarce (54% nursing vs.46% medical students;p<0.000).Notions on ODT were related with attitude toward the donation of one's own organs: those who considered their notions were good were more in favor then those who considered it scarce (88% vs.72%;p<0.000). CONCLUSION: Only 20% of Spanish medical and nursing students thought their notions on ODT were good.Having good knowledge is related to a favorable attitude towards ODT. Receiving specific information on the subject could improve their knowledge about ODT during their training.