Dendritic cells (DCs) are powerful antigen presenting cells that are involved in regulating immune response. Plasmacytoid dendritic cells (pDCs) are subtype of DCs that present in small quantity in the bone marrow, peripheral blood, and lymph nodes. They are important component of our immune system in normal condition and diseases. They activate T cells and play a critical role in immune tolerance. In this chapter we review the immunophenotypic features of pDCs and provide a practical protocol for pDCs enumeration in the peripheral blood and bone marrow samples.