Underwater sediments of two Dutch moorland pools, Gerritsfles and Kliplo, have been compared statistically with respect to total S and S-related sediment contents. Horizontal and vertical distribution of S in the two pools are significantly different from each other. Statistical analyses indicate that spatial variation of S in Gerritsfles is probably due to variation in inorganic S contents and in Kliplo due to variations in organically bound S. As evidenced by this study, a choice for a measurement unit like mass fraction (g g-1) or volumetric Mass (mg cm-3) is crucial for the interpretation of spatial variability. In spatial studies of sediment constituents, it is essential to express contents of these constituents in volumetric mass fractions, since spatial sediment patterns are often obscured by spatial variations in bulk density. Taking spatial variability into account may highly affect the quantification of S-budgets of pools or lakes.