This report describes synthesis and evaluation of novel cationic 99m Tc-nitrido complexes, [ 99m TcN (L)(PNP)] + (L = ma, ema, tma, etma and mpo; PNP = PNP5, PNP6 and L6), as potential radiotracers for heart imaging. is of particular interest due to its high initial heart uptake (1.81±0.35 %ID/g at 5 min postinjection), and long myocardial retention (1.99±0.47 %ID/g at 120 min postinjection). The heart/liver ratio of [ 99m TcN(etma)(PNP5)] + (6.06±1.48) at 30 min postinjection is almost identical that of 99m TcN-DBODC5 (6.01±1.45), and is >2 times better than that of 99m Tcsestamibi (2.90±0.22). Results from metabolism studies show that [ 99m TcN(etma)(PNP5)] + has no significant metabolism in the urine; but it does show significant metabolism in feces samples at 120 min postinjection. Planar imaging studies suggest that [ 99m TcN(etma)(PNP5)] + might be able to give clinically useful images of the heart as early as 30 min postinjection. [ 99m TcN(etma)(PNP5)] + is a very promising candidate for more pre-clinical evaluations in various animal models.