Introduction: Information provided by health care professionals is crucial to create a climate of social opinion. This is important in organ donation and transplantation (ODT), where the participation of the general public is essential to obtain organs. Objective: To determine the attitude toward the Law of Presumed Consent (LPC) among Spanish university students and to analyze their relation with attitude toward ODT. Methods: and design. The type of study was a sociologic, multicenter, observational study. The population included medical and nursing students in Spanish universities. Database of Collaborative International Donor Project was used stratified by geographic area and academic course. A validated questionnaire (Collaborative International Donor Project, organ donation and transplantation questionnaire in Spanish [PCID-DTO-RIOS]) was self-administered and completed anonymously. A sample of 9598 medical and 10,566 nursing students was analyzed (99% confidence and precision of ±1%) and stratified by geographic area and year of study. Results: Completion rate was 90%. Regarding attitude toward LPC, 66% of the students were against the law, whereas 34% accepted it. Of the students surveyed, 9% considered the law as a gesture of solidarity, 25% as an effective way of not wasting organs, 48% as an abuse of power, and 18% as offenses against the family. Those students who were in favor of LPC also had a more favorable attitude toward ODT (86% vs 76%; P < .001). Comparing groups, nursing students were less in favor of LPC than medical students (32% vs 36%; P < .000). Conclusion: Sixty-six percent of Spanish university medical and nursing students were against the LPC. The favorable attitude toward ODT is associated with considering the law as a gesture of solidarity or as an effective way of not wasting organs.