Background. 30 % of patients with heart failure have conduction disturbances most commenly seen as left bundle-branch block, and will benefit both hemodynamically and clinically from resynchronization therapy with biventricular pacemaker implantation. However, using the classical inclusion critera, 30 % of patients treated with resynchronization do not improve symptoms or activity level. Phase analysis of radionuclide ventriculography results in information about pattern of ventricular contraction which can be used to select responders among heart failure patients to resynchronization therapy. Material and methods. The study is based on 1264 radionuclide ventriculographies performed at Section of Nuclear Medicine, University Hospital North-Norway, during 1998–2006. The relationship between left ventricular ejection fraction (LVEF) and number of patients with ventricular dyssynchrony was investigated. 90 patients with no known heart problems were considered as reference values for synchrony data. Results. For patients with LVEF below 35 % the phase analysis resulted in 35 % and 36 % inter- and intra- ventricular dyssynchrony for female and male respectively. Interpretentation. Todays criteria for including patients to resynchronizing therapy is not good enough. Detection of ventricular dyssynchrony, using phase analysis of radionuclide ventriculography can be a better method to select responders for resynchronization therapy.