Purpose: To investigate the suitability of 144 Ce for both interstitial and intravascular brachytherapy applications. Methods and Materials: Monte Carlo calculations of radial dose rate distributions in water were performed for 144 Ce in a spring-shaped source and compared with two commonly used interstitial and intravascular sources, 192 Ir and 32 P. The numeric simulations were checked experimentally with a calibrated ionization chamber in a water phantom. Other source characteristics, such as half-life and specific activity, were also compared. Results: For interstitial brachytherapy, 144 Ce presents dosimetric advantages over 192 Ir in terms of higher dose rate at shorter distances and lower irradiation of organs outside the tumor. The source size and shape reduce the anisotropy and the number of dwell positions necessary. The longer half-life of 144 Ce might also be advantageous over 192 Ir. For intravascular brachytherapy, 144 Ce permits the treatment of larger arteries as compared with 32 P, compensates centering errors more effectively, and has a more suitable half-life. The experimental validation showed good agreement (within 10%) with the Monte Carlo simulated dose rate distributions. Conclusions: There are certain potential advantages of using 144 Ce as a source for both interstitial and intravascular brachytherapy. The basis for this finding is provided by the Monte Carlo radial dose rate comparisons with 192 Ir and 32 P, as well as by such characteristics as half-life and specific activity.