This book gathers selected papers from the KES-IDT-2020 Conference, held as a Virtual Conference on June 17–19, 2020.  The aim of the annual conference was to present and discuss the latest research results, and to generate new ideas in the field of intelligent decision-making. However, the range of topics discussed during the conference was definitely broader and covered methods in e.g. classification, prediction, data analysis, big data, data science, decision support, knowledge engineering, and modeling in such diverse areas as finance, cybersecurity, economics, health, management and transportation. The Problems in Industry 4.0 and IoT are also addressed. The book contains several sections devoted to specific topics, such as Intelligent Data Processing and its ApplicationsHigh-Dimensional Data Analysis and its ApplicationsMulti-Criteria Decision Analysis – Theory and ApplicationsLarge-Scale Systems for Intelligent Decision-Making and Knowledge EngineeringDecision Technologies and Related Topics in Big Data Analysis of Social and Financial IssuesDecision-Making Theory for Economics