The European Food Safety Authority (EFSA) asked the Panel on Plant Protection Products and their Residues (PPR Panel) to develop a Scientific Opinion on the relevance of dissimilar mode of action and its appropriate application for cumulative risk assessment of pesticides residues in food. The present opinion was preceded by three previous opinions of the PPR Panel (EFSA, 2008, 2009, 2013). The purpose of the present opinion was to assess the relevance of dissimilar modes of action (MoA) for cumulative risk assessment, to evaluate the existing methods for assessing chemicals acting by dissimilar MoA and to identify which methods need to be considered. The PPR Panel restricted its considerations of pesticide combinations with dissimilar modes of action to substances that produce a common adverse effect on the same organ/system. The PPR Panel noted that there is no case documented in the scientific literature where independent action provided more conservative predictions of combination effects than dose addition, and where at the same time independent action also produced accurate predictions. The use of independent action as an assessment concept for combination effects requires demonstration that modes of action of individual substances in a mixture are strictly independent, a condition that can rarely be met in practice. The PPR Panel also noted that there is no cumulative risk assessment method derived from independent action. The PPR Panel therefore recommends using cumulative risk assessment methods derived from dose addition also for the assessment of mixtures of pesticides with dissimilar modes of action, provided they produce a common adverse outcome. Pesticides that produce common adverse outcomes on the same target organ/system should be grouped together in CAGs, and their combined effects assessed by using the concept of dose addition as a pragmatic and conservative default approach for the purpose of assessing cumulative risk in relation to MRL setting or risk assessment of chemical mixtures in practice.