Professor Choi is among the leading experts on HIV infection in South Korea and has served on the board of directors of the Korean Society for AIDS, and the Korean Society for Infectious Diseases. His clinical and scientific work focuses on improving the local understanding of the HIV epidemic in South Korea and translational virology for understanding molecular characteristics of HIV.

Professor Choi has published over 100 peer-reviewed papers in various international journals and his work has developed a mathematical model for HIV infection among MSM in South Korea, which allows the predictions of HIV incidence and prevalence in the country. In addition, he has helped developed less costly but still accurate methods for monitoring virologic responses in HIV-infected persons.