In this study, we investigated the perceived professional needs of Korean science teachers majoring in chemical education, and examined their preferences for online and on-site inservice teacher training programmes. The results were also compared with those of preservice teachers. Participants were 120 secondary school teachers and 67 preservice teachers, whose majors were either chemical education or science education with emphasis in chemistry. A questionnaire consisting of a modified Science Teacher Inventory of Need and a section concerning respondents' demographic information and their use of the Internet was administered. In contrast to previous studies, the perceived needs of Korean inservice and preservice teachers were found to be very strong in all 30 needs assessment items, and their prominent needs were from all seven categories. Preservice teachers indicated significantly greater needs than inservice teachers on several items. Korean teachers generally tended to prefer online inservice to traditional on-site training programmes, although they still preferred on-site types of programmes in areas such as conducting laboratory sessions and demonstrating manipulative skills. Preferences for online programmes tended to be stronger among preservice teachers than inservice teachers, and among non-veteran teachers than in veteran teachers. Educational implications are discussed.