Measurements of single-kernel mass and volume made on healthy (control) and scab-damaged samples of grain of three winter wheat varieties never resulted in lower values of mean single-kernel density for scab-damaged grain. This finding, contrary to common opinion, can be explained as being a result of the comparable magnitude of relative decrease (due to infestation) of two features (mass and volume) that define single-kernel density. The discrepancy between results presented in this paper (kernel volume was determined with an air pycnometer) and the results in some other reports (liquid pycnometers used) can result from the different methods applied for kernel volume measurements: when a liquid medium is used the surface tension effect tends to overestimate the volume, especially for scabby kernels that are known to be shrivelled ie possessing voids and pores at the surface that the liquid cannot penetrate. As a consequence kernel density of scabby kernels can be significantly underestimated.