Naturally occurring praseodymium (59Pr) is composed of one stable isotope, 141Pr.
All of the remaining radioactive isotopes have half-lives that are less than six hours and the majority of these have half-lives that are less than 33 seconds.
The isotopes of praseodymium range in atomic weight from 120.955 u (121Pr) to 158.955 u (159Pr).
The primary decay mode before the stable isotope, 141Pr, is electron capture and the mode after is beta decay.
The primary decay products before 141Pr are element 58 (cerium) isotopes and the primary products after are element 60 (neodymium) isotopes.