Urban tree risk assessment and mitigation is a very human endeavor which is influenced by professional experience, risk perception, and risk tolerance. While arborists and other tree risk assessors document all of the risk factors they see in an effort to provide their clients a comprehensive assessment of a tree and its surroundings, the homeowner or property manager ultimately determines what mitigation measures are adopted. This study assessed perceived risk for an array of photographed urban tree scenarios designed to address specific aspects of target, likelihood of failure, and consequences of failure. While risk ratings of all three respondent groups (i.e. non-professionals, professionals, and advanced professionals) were influenced by the presence and severity of a tree defect, only advanced arborists were influenced by a risk attribute – proximity to target. Findings highlight the need to educate both the public and tree care professionals.