In paper making, surface properties are of major importance for the printability of the final paper. It is therefore essential to identify the fundamental fibre properties causing surface problems in order to be able to improve the final paper. It is well known that the amount of intact fibres is higher in TMP than in GW. It is also believed that thick-walled intact fibres, especially large-diameter fibres, are negative for surface properties. When TMP and GW for magazine grades are analyzed with respect to fibre dimensions by scanning electron microscopy (SEM) images of fibre cross-sections, far more thick-walled fibres are found in TMP than in GW. It is therefore probably more important in quality control to focus on thick-walled fibres for TMP than for GW. On the other hand the amount of shives is considerably higher for GW than for TMP and such material is also negative for the surface properties. Both shives and fibre dimensions have been analyzed using cross sectional SEM images of Bauer McNett >50 fractions in a study including screening, cleaning and reject refining of a GW pulp for magazine paper. The same analysis was also conducted for a number of different final GW pulps and one TMP used for magazine paper. Slotted screens are commonly used today for successfully separating large shives, but are not capable of removing smaller shives. It is obvious that most of the shives measured in a Somerville laboratory screen (0,15mm slots) will be separated in the slotted screens. However, measuring shives in cross sections shows that only a small amount of the shives is separated in the screens. Even if the pulp has been treated in both screens and cleaners, approximately one third of the shives still remain. This indicates how difficult it is to get rid of shives in the screen room, and therefore it is critical to minimize the amount of shives in the grinding process. Despite the fact that Somerville shive measurements indicated no significant difference between different commercial mechanical pulps for magazine paper (GW and TMP), major differences in shives measured in cross sections of the fibres were found. The amount of shives was higher compared to the amount of large thick-walled fibres for most GW pulps, but for TMP it was the opposite in this comparison. It is therefore probably important to focus on reduction of shives in GW pulping and on reduction of thick-walled fibres for TMP. In mechanical pulping it is important to manufacture a pulp with as low an amount of shives as possible, especially if the screen room only has screens.