The article presents a particular mechanism of political decision making in contemporary democratic systems. It is called here 'ad hoc democracy'. This notion refers to the phenomenon of making political decisions (that are general and abstract) on the basis of premises that are individual and situational. After defining ad hoc democracy, the author reconstructs a typical scenario of the phenomenon, demonstrates selected examples of ad hoc democracy and discusses its main consequences. The analysis of ad hoc democracy construction process follows. The main cause of ad hoc democracy is defined as the interference of internally inconsistent logic of actions taken by three types of actors in political sphere: media, society (treated as an audience) and political decision-makers. In the last part of the article it is hypothesized that the systems experiencing rapid social changes and democratization processes are particularly prone to the emergence of ad hoc democracy. The hypothesis is justified and substantiated by referring to an example of Poland during the systemic transformation process.