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. To determine the attitude toward the Law of Presumed Consent (LPC) among Spanish university students and to analyze their relation with attitude toward ODT. 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. 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). 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. •Sixty-six percent of Spanish university medical and nursing students were against the Law of Presumed Consent.•Nursing students were less in favor of the Law of Presumed Consent than medical students.•A favorable attitude toward organ donation and transplantation is associated with the views that LPC is a gesture of solidarity or an effective way of not wasting organs.