How clients' during-treatment motivations relate to their perceptions and impressions of methadone maintenance treatment: A multilevel analysis of a cross-sectional survey in Guangdong Province, China.

•There is a need for improving during-treatment motivation among Chinese methadone maintenance treatment (MMT) clients.•Besides education, clients’ perceptions and impressions of MMT relate to motivation.•Supportive family assistance and closing time relate to motivation at clinic level.