The principle of equal treatment or non-discrimination is a general principle of European law which presupposes that comparable situations or parties in comparable situations are treated in the same way. The principle of equal treatment is only infringed when comparable situations are treated differently or different situations are treated identically, unless such treatment is objectively justified.

Thus, the allocation of the same starting amount of the fine to undertakings of different sizes on the grounds that they are included in the same category, is not contrary to the principle of equal treatment where this difference is objectively justified by the greater importance attached to the nature of the infringement than to the size of the undertakings when assessing the gravity of the infringement.

On the other hand, the Commission violates the principle of equal treatment in concluding that a firm had not played an exclusively passive role in the infringement while at the same time giving the benefit of that attenuating circumstance to another undertaking whose role in the infringement was not notably different and which, furthermore, had entered the market earlier. Lastly, an undertaking on which a fine has been imposed for its participation in a cartel cannot request the annulment or reduction of that fine, on the grounds that another participant in the same cartel was not penalized in respect of a part, or all, of its participation in that cartel. In effect, the principle of equal treatment in the fixing of the fine may not be invoked by an undertaking to benefit from an unlawful act committed in favor of another participant in the cartel.