This paper presents a user-centered design methodology for Decision Support Systems (DSSs), which is specifically built to face the socio-technical gap that often impedes DSS acceptability by end users in real work environments. The methodology has been experimented in two case studies in the field of healthrelated emergencies, namely earthquake and pandemic flu management. Methodology application and results are described with specific focus on the phases of requirement analysis and system evaluation. Keywords. User-centered design, decision support systems, requirement analysis, evaluation, socio-technical gap, emergency management.