The mass distribution index of the Geminid, Quadrantid, Arietid, Eta Aquariid, Orionid and South Delta Aquariid meteor showers have been measured using data from 2007 to 2010 from the Canadian Meteor Orbit Radar (CMOR). Single-station data from the 29.85-MHz system were used to find mass index as a function of solar longitude, and to compare separate years of showers. The variation in mass index with solar longitude can provide information on the structure of the stream and how the structure changes with time. The Geminids and Quadrantids were the most prominent showers seen by CMOR, and had peak mass indices of 1.65 and 1.55, respectively. They had clear, strong peaks and little year-to-year variation. The other showers had slightly higher peak mass indices and a greater variability, even though a more sporadic contamination, which might have affected the results.