In this paper we study the jump-diffusion CIR process (shorted as JCIR), which is an extension of the classical CIR model. The jumps of the JCIR are introduced with the help of a pure-jump Lévy process (J t , t ≥ 0). Under some suitable conditions on the Lévy measure of (J t , t ≥ 0), we derive a lower bound for the transition densities of the JCIR process. We also find some sufficient conditions under which the function V (x) = x, x ≥ 0, is a Forster-Lyapunov function for the JCIR process. This allows us to prove that the JCIR process is exponentially ergodic.