BACKGROUND One of the mechanisms for periprocedural neurologic events in carotid artery stenting (CAS) is catheter manipulation within the aorta and supraaortic arteries causing plaque embolization. Therefore, the present analysis sought to determine risk factors for embolic particle dimensions and their relationship with adverse clinical events after CAS. METHODS Between 1999 and 2015 embolic protection devices (EPD) of a total of 944 CAS procedures were evaluated regarding the occurrence and size of captured particles. RESULTS Particles were found in 819 of 944 (87%) EPDs. Larger particles were detected in procedures using open cell stents (150±282μm vs. 107±177μm; p=0.005) and longer stents (≥40mm) (165±315μm vs. 122±215μm; p=0.026). With increasing learning curve, particle size was continually reduced (168±282μm in the first third of the cohort vs. 127±309μm in the second third vs. 108±114μm in the last third; p=0.009). Longer stents and use of Acculink stent were found to be independent predictors for particle diameter. In patients who died or sustained a stroke during long-term follow-up (median 5.5years [IQR 2.6-7.9]) significantly larger particles were captured during CAS compared to those patients with an uneventful follow-up (160±330μm vs. 121±195μm; p=0.047). CONCLUSIONS In the vast majority of CAS procedures particles could be retrieved from the EPDs used. Procedural characteristics such as stent type and stent length were associated with larger particles.