Objective: We examined the usefulness of light-chain restriction (LCR) on immunocytochemical double staining (IDS) for cytological diagnosis. Study Design: We investigated LCR on IDS in 40 patients with proliferative lymphatic disorders (23 with B cell lymphoma, 13 with reactive lymphoid lesions, 2 with T cell lymphoma and 2 with Hodgkin’s lymphoma). In addition, the results of flow cytometry (FCM) were compared in 34 of these patients. Results: On IDS, LCR was detected in 21 of 23 patients (91.3%) with B cell lymphoma. On FCM, it was detected in 15 of 21 patients (71.4%) with B cell lymphoma. Neither IDS nor FCM showed LCR in any patients with reactive lesions, T cell lymphoma or Hodgkin’s lymphoma. Conclusion: IDS facilitated the detection of LCR with a single specimen under morphological observation. The application of this procedure may improve the accuracy of cytological diagnosis.