BACKGROUND: Patients with chronic health conditions risk aggravation of their health status due to reduced access to health services during the COVID-19 related lockdown. OBJECTIVES: To investigate the impact of Belgian COVID-19 measures on general health status (i.e. worse or stable/better) of patients, adult and pediatric, with chronic health conditions and how this change in health status relates to personal and health behavior-related factors. DESIGN: A cross-sectional study using an online survey was conducted during the first COVID-19 related lockdown in Belgium. METHODS: Associations between change in health status since the lockdown and (change in) personal and health behavior-related factors (including physical activity, access to health-care services and social activities) were investigated. RESULTS: In adults (n = 561), almost all personal factors, including feelings of distress, depression, anxiety, somatization, and low self-efficacy, were significantly worse in patients with a worse health status during the lockdown (n = 293, 52%) compared to patients reporting a stable/better health status (p