The thesis elaborates a positive theory of central bank accountability. Fulfilling the call for institutional solutions to guarantee the democratic legitimacy of policy-making by independent authorities, accountability is modeled as the ex-post assessment of the central bank performance by political principals. The charecteristics of the economy and the preferences of the population determine accountability needs. Modelling accountability and transparency as decision taken by rational policy-makers involved in a strategic interaction, the thesis also shows that the decision of the government to impose accountability requirements might lead monetary authorities to be transparent, i.e, to reveal their preferences. As to the role of fiscal discipline in central bank accountability, the thesis points out that the assignment of a specific mandate to fiscal authorities, clarifying mutual responsabilities and enhancing transparency about each authority's area of responsability, ultimately makes both policy makers accountable for implementing a socially optimal policy mix