This book constitutes the refereed proceedings of the 18th International Conference on Economics of Grids, Clouds, Systems, and Services, GECON 2021, in September 2021. Due to COVID-19 pandemic the conference was held virtually hosted by the Libera Università Maria SS. Assunta (LUMSA), Rome, Italy. The 7 full papers and 2 short papers presented in this book were carefully reviewed and selected  from 41 submissions. In addition, this book includes 8 work-in-progress papers and 2 extended abstracts. Chapters “AI Technologies and Motives for AI Adoption by Countries and Firms: A Systematic Literature Review�; “Knowledge Management Framework for Cloud Federation�; “Architecture for Orchestrating Containers in Cloud� and “Towards Software Compliance Specification and Enforcement using TOSCA� are available open access under a Creative Commons Attribution 4.0 International License via link.springer.com.