Significant imbalance in the rights and obligations of the parties to a consumer contract term is, together with good faith, a fundamental pillar of substantive protection against unfair terms. It is the primary tool provided by Council Directive 93/13/EEC of 5 April 1993 on unfair terms in consumer contracts with a view to mitigating differences in bargaining power between professional traders and consumer on the ever-expanding capitalistic market within the EU. The paper comprehensively reviews the meaning of the “significant imbalance” element by reference to a cross-section of judgments handed by the CJEU and Polish courts. Generally, albeit with a few notable exceptions, the former court has engaged in a subjective-objective exercise aimed at discovering what the balance of rights and obligations would have been between the parties in the particular dispute at hand had it not been for the purportedly unfair clause. Besides that, the requirement has been utilized to impose ad bolster a host of information duties levied on traders so that protection is extended to cases where the consumer is unaware of their rights or are deterred from enforcing them due to procedural obstacles or prohibitive costs of judicial or administrative proceedings. The requirement of significant balance, rooted in the idea that the disproportion of market power between the parties to a disputed term necessitates government or judicial intervention to achieve or restore contractual equilibrium, is shown from a plethora of angles: its ideological foundations, practical connotations, its emphasis on consumer vulnerability and approach to economic power. Assistance and inspiration re gleaned from Polish jurisprudence where numerous questions either unanswered by the CJEU or left to the consideration of national courts, particularly the relation between reasonableness, on the one hand, and significant imbalance and good faith on the other, as well as between significant imbalance and good faith, have been tackled.