Technological and chemical analyses allowed to determine the type of painting materials and the technical structure of two wall paintings in the main nave of the church of St. Mary in Torun (Poland). Stratigraphy of mortars, white-wash and paint film has been determined. Three (mortar-white wash paint) or four-layer (mortar-2 white wash layers-paint film) structures were found. The mortars examined show a variable binder to filler ratio, the binder being of basal or, locally, of porous type. Natural aggregate of fluvial origin is the main filler component. Chalk white-washes containing carbohydrates, present a good adhesion to mortars, which indicates that they were put on wet mortar. The colour scale of the examined paintings is the following: chalk, ochre, red lead, iron red, azurite, malachite, raw umbre, carbon black. The binder of the paint films contains corn glue with an admixture of unidentified protein-like substance.