Cyclic adenosine 35-monophosphate (cAMP) and cyclic guanosine 35-monophosphate (cGMP) are critical intracellular messengers involved in transduction of signals generated by a wide variety of extracellular stimuli, including growth factors, cytokines, peptide hormones, light and neurotransmitters. These messengers modulate many fundamental biological processes, including myocardial contractility, platelet aggregation, vascular smooth muscle relaxation, proliferation and apoptosis, etc. Cyclic nucleotide phosphodiesterases (PDEs) catalyze the hydrolysis of cAMP and cGMP, and are important in regulating intracellular concentrations and biological actions of these signal-transducing molecules. These enzymes contain at least 11 highly regulated and structurally related gene families (PDE1-11). In this review, we will discuss some general information of PDEs and then focus on PDE3 gene family, including the molecular biology, structure, function and potential as therapeutic targets. Furthermore, we show the possibilities of PDE3 as therapeutic targets in malignant tumor cells and salivary gland.