Solitary plasmacytoma of the paranasal sinuses are uncommon neoplasms of B lymphocyte origin. They comprise one per cent of all head and neck tumours of the upper respiratory tract. They can be solitary plasmacytomas of the bone (SPB), an extramedullary plasmacytoma or a local manifestation of multiple myeloma. Conversion to multiple myeloma happens more frequently in SPB. Radiotherapy is the common modality of treatment with, or without, adjuvant chemotherapy. Extramedullary plasmacytoma carries a better prognosis than a solitary plasmacytoma of the bone. We report four cases of solitary plasmacytoma of the bone and an extramedullary plasmacytoma of the paranasal sinuses and soft palate.