The paced 12-lead ECG is a valuable tool in the assessment of patients with pacemakers. Ideally it should be recorded routinely at the time of implantation and during follow-up. It has become particularly important in
patients undergoing cardiac resynchronization. Vector analysis of 12-lead ECG allows diagnosis of localization and possible dislocation of stimulating leads. The multiplicity of clinical situations highlights pitfalls of using a single ECG lead in the overall evaluation of pacemaker patients. The design of programmers capable to register 12-lead ECG would improve the care of pacemaker patients.