<p>Photocatalytic technology based on heterogeneous catalysis is well known as an effective and prospective advanced oxidation process (AOP) for organic pollutant destruction. However, owing to non-selective degradation mechanisms and high reactivity of radicals, such a photocatalytic process is typically believed to be intrinsically non-selective. In the case of complex environmental mixtures with various co-occurring contaminants, the non-selective nature of the process may lower its efficiency and consume higher energy. Recent advances have shown increasing interest in preferential photodegradation by which selected target pollutants are removed more efficiently than others. This review presents a critical and quantitative assessment of preferential photodegradation in heterogeneous photocatalysis. To facilitate a better comparison of results obtained in different studies, both kinetic-based and conversion-based definitions of selectivity are clearly defined. The possible sources of selectivity in heterogeneous photocatalysis include competitive adsorption, surface reactions’ kinetics, mass transport effects, and chemical structures of pollutants. Moreover, the effect of operation parameters like pH, inorganic ions, irradiation condition, and exposure time on selectivity is critically discussed. Finally, novel catalyst design and photocatalytic reactor design techniques like surface modification, heterojunction, shuttle effect, and nanopore structure manipulation are proposed with selected illustrative examples. Current limitations in terms of the definition of selectivity criteria and reliance on idealized experimental conditions are also discussed.</p>