The paper examines the workload perceived by Air Traffic Control Officers (ATCOs) and pilots during Continuous Descent Operations (CDOs), applying closed and open path procedures. CDOs reduce fuel consumption and noise emissions. Therefore, they are supported by airports as well as airlines. However, their use often depends on pilots asking for CDOs and controllers giving approval and directions. An adapted NASA Total Load Index (TLX) was used to measure the workload perception of ATCOs and pilots when applying CDOs at selected European airports. The main finding is that ATCOs' workload increased when giving both closed and open path CDOs which may have a negative impact on their willingness to apply CDOs. The main problem reported by pilots was insufficient 'Distance-to-Go' information provided by ATCOs. The workload change is important when considering the use of CDOs.