CleanSeaNet is a satellite-based monitoring service operated by the European Maritime Safety Agency (EMSA), aimed at detecting oil spills and other forms of marine pollution across European Union waters. As one of the key operational tools supporting maritime surveillance and environmental protection, the service provides national authorities with near-real-time information that can be used for both immediate response and long-term policy development. This study evaluates and compares the performance of individual satellites contributing to the CleanSeaNet system, focusing on their effectiveness in identifying surface-level pollution events. Using a comprehensive dataset collected over the past five years, detected spills were categorised according to the confirmation method employed—such as aerial surveillance, vessel reports, or follow-up inspections—and subsequently classified as either real pollution events or false positives. The primary objective of this analysis is to assess the detection accuracy of each satellite across a range of spill types, while also identifying potential patterns in reliability. The findings indicate that satellite performance is not uniform. Instead, significant variations emerge that support the hypothesis that detection efficiency depends on multiple interrelated factors, including sensor technology, orbital characteristics, and prevailing environmental conditions such as sea state or wind. These insights provide valuable guidance for optimising monitoring strategies and improving the overall robustness of CleanSeaNet.