Owing to the coronavirus disease 2019 (COVID-19) pandemic, understanding how to hold future online academic conferences effectively is imperative. We assessed the impact of COVID-19 on academic conferences, including facilities and settings for attendance, participation status, cost burden, and preferences for future styles of holding conferences, through a web-based questionnaire survey of 2,739 Japanese medical professionals, from December 2020 to February 2021. Of the participants, 28% preferred web conferences, 60% preferred a mix of web and on-site conferences, and 12% preferred on-site conferences. Additionally, 27% of the presenters stopped presenting new findings at web conferences. The proportion of participants who audio-recorded or filmed the sessions, despite prohibition, was six times higher at web than face-to-face conferences. Since the COVID-19 outbreak, the percentage of participants attending general presentations decreased from 91 to 51%. While web conferencing offers advantages, these are offset by a decrease in presentations pertaining to novel findings and data.