This is the first national survey study in South Korea investigating the relationship between suicide lethality and the clinical information of suicide attempters. An interview questionnaire was used to assess their sociodemographic factors, medical and psychiatric information, and two suicide scales, the Columbia–Suicide Severity Rating Scale and the Suicide Intent Scale. Suicide methods were categorized as low and high lethality; low lethality covered drug overdose or self-cutting behavior, and high lethality covered all other methods. High and low lethality suicide method groups were significantly different in demographic, medical, and psychiatric factors. The two scale score distributions differed significantly across two groups, and the difference was also valid for the subcategory analyses of the Suicide Intent Scale. Multiple factors such as older age, male sex, no previous psychiatric history, and previous suicide attempt, as well as high suicide intent by means of suicide scale, affect selection of suicide method of high lethality.