The role of catheter ablation in the treatment of ventricular arrhythmias has been changing in the last decade, and this form of therapy now aims at curing multiple ventricular tachycardia morphologies and complex substrates in patients with structural heart disease (post-infarction and idiopathic dilated cardiomyopathy). Under these circumstances, conventional mapping is not feasible and accurate, and the development of new diagnostic methods has become necessary. The non-contact mapping system has been introduced to study the activation pattern of any ventricular arrhythmia by a "single-cycle" analysis, and has brought to the characterization of unstable and of non-sustained forms of arrhythmia. The evaluation of the arrhythmogenic substrate has similarly become more precise by the more common use of the electroanatomic mapping (CARTO), which is being applied to identify areas of scarred tissue responsible for ventricular arrhythmias, to map stable tachycardias and to validate the creation of a line of block. By means of this technological advancement, the identification of critical isthmi and deep intramural circuits has also led to new ablation strategies, frequently simplifying the procedure and minimizing complications.