Accountability in constitutional law may lead to confusion with other categories: political and legal responsibility, audit, financial control. A need to develop this concept is particularly urgent regarding judiciary as a branch of public authority. Accountability, defined as the capabilities of principals to judge the performance of their agents, has two main requirements: a relationship between Principal and Agent, and conclusive Agent’s report on the performance of the assigned competences. Within Judiciary there are two Agents: judicial branch accountable for its effectiveness, and judges accountable for their decisions. But manifestations of accountability lead to some paradoxes, eg. Effectiveness cannot be measured using quantitative methods. Accountability of judges, classically guaranteed by ‚open justice’ is exposed to risks of media polarization and populism. The judicial decision as communicative acts are also exposed on the risk of communicative disturbances (noises).