During exploitation different effects influence printed textile products and one of the most common is washing treatment. It causes modification of textile structure and textile fibres. The aim of this research is to determine the influence of the washing treatment, the washing treatment temperature and characteristics of printed material on print quality parameters of screen printed cotton knitted textile materials. It will be obtained using spectrophotometric analysis and macro non-uniformity analysis via the mottling index. The research results show that increasing the number of washing treatments, and also increasing of washing temperature, causes an increase of colour difference between washed and unwashed samples. It also shows that substrate characteristics have great influence on colour differences. Besides that, washing treatment also causes noticeable changes of print mottle, which are, again, also dependent on substrate characteristics.