Risk assessment is the process of determining the likelihood or threat of a damage, injury, liability, loss, or other negative occurrence that is caused by external or internal vulnerabilities and that may be neutralized through preventive action. More precisely, risk assessment is the systematic prospective analysis aimed at defining, as quantitatively as possible, the potential loss of life, personal injury, economic loss, and property damage resulting from natural and/or anthropogenic hazards, by assessing the exposure and vulnerability of people and property to those hazards. The risk assessment procedure, developed in the Mountain Risks project, is based on the following five steps: (1) Identification and analysis of the specific types of hazards that could affect a territory and its community; (2) Definition of the spatial and temporal likelihood of the damaging events considered in the analysis as well as their magnitude; (3) Inventory of the assets and study of the social and economic features of the study areas; (4) Assessment of vulnerability, evaluating all the hazard consequences for each dimension composing the systems at risk (physical/functional, economic, socio-cultural, ecological/environmental and; political/institutional); (5) Evaluation of the prospective cost of damage or costs avoided through mitigation strategies. Vulnerability assessment plays a crucial role both in 'translating' the assessed level of hazard into an estimated level of risk and in providing leading information in mitigation planning processes and emergency management strategies. Under this perspective, it is really difficult, or even impossible, to address risk assessment without assessing vulnerability first and it appears unquestionable that a multi-disciplinary approach is required in vulnerability assessment studies. In this section, the different components (dimensions) of vulnerability are analyzed, both theoretically and practically, and then different methodological approaches, applications and solutions are provided.