Ubiquitin-dependent proteasomal degradation is one of the major pathways of non-lysosomal protein degradation in the cell. The ubiquitination process involves several enzymatic reactions and includes the following enzymes: E1--activating, E2--conjugating, and the third--E3--ligating enzymes. E3 ligases determine the specificity of ubiquitination reaction, i. e. what target protein will be subjected to the covalent modification by ubiquitins. The p53b tumor suppressor protein is one of the most intensively studied over the past several decades. Regulation of its activity is a complex and multi-level process that involves many factors. Ubiquitination is one of the major post-translational modifications of p53, and plays a fundamental role in the control of p53 function, its amount, activity and subcellular localization. This review is focused on p53-specific E3 ubiquitin ligases that are potential targets for cancer therapy using small molecule inhibitors.