Smartphones permeate everyday life, and its ownership is considered to be a norm especially among young generation. However, a majority of users are experiencing negative aspects of smartphone use which ranged from conflicts with daily lives (e.g., social interactions, work/study, and sleep disturbance) to health problems (e.g., techno-stress, and attention deficits). To deal with these concerns, users often attempt to regulate smartphone use by actively managing its use under various situations. In some cases, they even decided to become a non-user, by downgrading to feature phones. In this work, we report our survey results on the current practices of smartphone non-use and discuss HCI-related research issues on the interaction design for supporting smartphone non-use.