We aimed to explore associations between risk items scored Don’t know, indicating lack of information, and subsequent violence when using a 10 item risk screen (Violence risk screening - 10; V-RISK-10) in a sample from three acute psychiatric wards (N = 1435). V-RISK-10 was scored at admission and before discharge. Violence was recorded during hospital stay and three months post - discharge. For most items, a significant proportion of patients were scored Don’t know at admission, and Don’t know scores at admission were significantly associated with inpatient and post-discharge violence. Substantially fewer risk items were scored Don’t know before discharge, and for most items, Don’t know scores were not significantly associated with post-discharge violence. These preliminary findings are relevant for acute psychiatric admissions when information on risk factors may be sparse and indicate that lack of information at time of admission should be taken into consideration in violence risk assessments.