In the present work, the study of semiconducting Ce(1-x)MXO2 (M=Ru, In) solid-solutions nanostructures with application to gas sensors is addressed. Nanostructured powers were prepared by means of the sol-gel route. The electrical resistance of obtained materials under different conditions of time, concentration and temperature in CO presence was tested. These systems were characterized using x-ray diffraction, SEM microscopy and surface area measurements. The solid solutions demonstrated good sensorial response at low temperatures, as well as fast response as a function of time. Our results show that these novel materials can be potentially applied as gas sensors.