During the recent years, g-C3N4/TiO2 composites have been regarded as efficient photocatalysts for the removal of air pollutants. The combination of these materials gives excellent photocatalytic performances, as each ones advantage covers the disadvantages of the other. In the present study, g-C3N4/TiO2 heterostructures were synthesized by mixing chemically exfoliated g-C3N4 with commercial TiO2 P25 in different ratios and were examined for the removal of NOx and acetaldehyde under visible-light irradiation. The results of photocatalytic tests in correlation with the EPR experiments revealed that heterostructures containing higher amount of TiO2 are efficient in systems where the attack of hydroxyl radicals prevails (acetaldehyde), while dominant g-C3N4 content provides effectiveness in systems where superoxide radical anions play the key role (NOx). This outcome is directly coupled with the energy positions of conductionand valence-band edges of each material.