In the context of carbon capture utilization and storage (CCUS), reuse of existing onshore and offshore pipelines may be an attractive alternative to installing new pipelines. Through different work packages, the ongoing CO2SafePipe Joint Industry Project (JIP) addresses identified challenges when repurposing pipelines for the transport of carbon dioxide in both gas and dense phases. This initiative aims to ensure that a repurposed pipeline adheres to the same stringent safety and performance standards as new pipelines. Dense phase condition has historically been the preferred option for pipelines specifically designed for transporting larger quantities of carbon dioxide. When considering the reuse of existing pipelines for transporting carbon dioxide, dense phase may not always be a technically viable option due to limitations from the original design of the pipeline planned for reuse. This paper delves into the specific challenges of re-qualifying pipelines for transporting carbon dioxide in gas phase, identifying key considerations, opportunities and limitations. Special attention is given to pipeline operating envelope, product composition, material properties, integrity management, and safety considerations.