Abstract: The post-consumer plastic packaging waste management in Flanders was analyzed by performing a retrospective material flow analysis, covering an extensive period from 1985 to 2019. In addition, a prospective material flow analysis of 32 improvement scenarios was performed, based on expected changes in the waste management system. Mass recovery rates were calculated based on different interpretations of the calculation rules. Moreover, various cascading levels were identified to differentiate between the quality level of the secondary applications. The mass recovery rate including only recycling evolved from a value of 0% in 1985 to 31% in 2019 and could be increased to 36-62% depending on the improvement scenario selected. However, the different interpretations of the calculation rules led to a variation of up to 20 and 41% on this mass recovery rates for the retrospective and prospective analysis, respectively. The introduction of monostream recycling for additional post-consumer plastic packaging flows, such as low-density polyethylene, did not lead to increasing mass recovery rates, if no differentiation for the cascading levels was made. The Belgian recycling target of 65% for 2023 will be challenging if the strictest calculation method needs to be followed or if the improvements in the Flemish postconsumer plastic packaging waste system do not follow the best-case collection scenarios under the given assumptions. To harmonize the calculation and monitoring of these targets, clear calculation rules need to be accompanied with a harmonized monitoring system over the entire waste management system.