The wall paintings in the Roman thermes at Campo Valdes in Gijon (Spain) can be set chronologically in the first half of the 2nd century BC. The conservation and restoration works had consisted in treatments in situ and reset/rebuilding of found fragments on a new support. The methodology of conservation and restoration followed is: control of environment (atmospheric humidity and temperature), sampling and analysis of original materials and mortars, graphical documentation, cleaning of fragments and walls, rendering protection, treatments and consolidation, execution of an intermediate layer between the back of the paint and the new support, setting of fragments on a rigid support and reintegration of losses and final protection treatment. The support mortars of the different thermes walls are similar. They are built with stone blocks and renderings. The original mortars were prepared with lime and sand mixes. The aggregate is composed of quartz and calcium carbonates. The repairing mortars were selected from original mortar compositions establishing the compatibility criteria. The pigments identified were: calcium carbonate, red and yellow ochre, carbon black, Egyptian blue and green earth. The study of binding media has permitted the identification of oil, colophony (rosin) and calcium soaps in the samples. Rosin pitch or fig-tree latex are also hypothetical components of the binding media of paintings.