This paper provides a critical and the most up-to-date review and analysis of published studies of geological carbon dioxide (CO2) storage resources in Pennsylvania and the surrounding region through (a) carefully examining the assessments by different agencies, including the methodology, assumptions, and storage resources; (b) reconciling the different assessments on the basis of our understanding of the geology of Pennsylvania and the region; and (c) clarifying the storage resources of Pennsylvania and the region on the basis of a classification system that was published by Society of Petroleum Engineers in 2017. Total CO2 storage resources are 756 Gt, 8 Gt, 0.8 Gt, and 104 Gt in saline formations, depleted oil and gas reservoirs, coals, and the Marcellus shale, respectively in Pennsylvania (Dooley et al., 2005; Godec et al., 2013b). Contingent (Technically accessible) CO2 storage resources in Pennsylvania ranges from 26 Gt to 30 Gt in saline formations, depleted oil and gas reservoirs, coals, and the Marcellus shale (US-DOE-NETL, 2015; Edwards et al., 2015). Further assessment of geological CO2 storage in organic-rich shales (e.g. the Marcellus shale in Pennsylvania) is needed. The new knowledge from this review is crucial and helps governments, industries, researchers, and policymakers to understand and manage carbon capture utilization and storage (CCUS) economy, projects, and policies in Pennsylvania.