OBJECTIVE: Many studies have reported the importance of preventing sexually transmitted infections (STIs), such as syphilis and AIDS, in young adults, and it is crucial to compare and analyze impressions of syphilis and AIDS in young adults. Therefore, the present study used a text-mining analysis to compare impressions of syphilis and AIDS in students at a healthcare professional university. METHODOLOGY: This study involved 174 students from a healthcare professional university (94 males, 80 females, aged 20.2 ± 1.2 years). Participants were surveyed on their sex, age, awareness of changes in syphilis and AIDS patient numbers in Japan over the past decade, sexual experience, and contraceptive use. Additionally, open-ended questions were asked, such as, "Please describe your impressions and thoughts about syphilis" and "Please describe your impressions and thoughts about AIDS." The responses were then analyzed using text-mining techniques. RESULTS: Among all participants, 59 males (62.8%) and 47 females (58.8%) had sexual experience. Of those with sexual experience, 47 males (79.7%) and 38 females (80.8%) always used contraceptives. The text-mining analysis revealed that frequent terms for syphilis included "infection", "image", "nature", "sex act", "disease", and "frightening", while those for AIDS were "infection", "image", "disease", "impression", "be cured", and "frightening". The term "be cured" was a characteristic word for AIDS. The term "frightening" was common for syphilis in females and for AIDS in males and was also notable for syphilis and AIDS in those without sexual experience or those who did not always use contraceptives. CONCLUSIONS: The comparison of impressions of syphilis and AIDS in students at a healthcare professional university using a text-mining analysis revealed differences between the two diseases. The term "be cured" was a characteristic word for AIDS, while "frightening" was common for syphilis in females and for AIDS in males.