A comparison of ^99mTc- CQDO and ^99mTc-CQDO-MeB has been made for biodistribution and pharmacokinetics. ^99mTc-CQDO and its adducts of methaneboronic acid ^99mTc-CQDO-MeB were prepared by the reduction of Na^99mTcO₄ with SnCl₂·2H₂O in aqueous solution. Radiochemical purity of ^99mTc-CQDO and ^99mTc-CQDO-MeB determined by TLC were over 95% after extraction. Biodistri-butions of ^99mTc-CQDO and ^99mTc-CQDO-MeB in mice demonstrated that both of them could be easily absorbed by myocardium, and the peak uptake of each were 10.83±2.2% ID/g and 11.84±1.69%ID/g, respectively. ^99mTc-CQDO showed rapid clearance from myocardial tissue while ^99mTc-CQDO-MeB had long retention in heart muscle. The myocardial uptake of ^99mTc-CQDO was only 5.88±1.66%ID/g at 10min. and the uptake of ^99mTc-CQDO-MeB was 7.42±0.17%ID/g at 60 min. The elimination of each from blood has a biexponential pattern, the first T_1/2 is 1.38 and 1.5 min, respectively. The partition coefficient of ^99mTc-CQDO and ^99mTc-CQDO-MeB were 20 and 25 at pH 7.40, respectively.