Thisbook gathers a selection of refereed papers presented at the 4th InternationalSymposium and 26th National Conference of the Hellenic Operational ResearchSociety. It highlights recent scientific advances in operational research andmanagement science (OR/MS), with a focus on linking OR/MS with other areas ofquantitative methods in a multidisciplinary framework. Topics covered includeareas such as business process modeling, supply chain management, organizationperformance and strategy planning, revenue management, financial applications,production planning, metaheuristics, logistics, inventory systems, and energysystems.