Gene array studies on follicular lymphoma (FL) have associated non-malignant tumor-infiltrating immune cells with patient survival. We examined the role of such cells detectable by immunohistochemistry in a tissue microarray, focusing on plasmacytoid dendritic cells (pDCs). These cells physiologically produce interferon-α, which has been used in the therapy of FL. High numbers of pDCs are associated with increased survival, and so are high numbers of CD3+ T cells. The regular distribution of pDCs within T cell areas is reflected by a weak but significant correlation between pDCs and T cells. However, in multivariate Cox models, CD123 proved to be an independent prognostic factor. These findings support the hypothesis of an association of pDCs with better prognosis by producing interferon. Furthermore, due to a linear relationship between pDCs and survival shown by means of Kaplan-Meier plots, immunohistochemical staining of CD123 could serve as a prognostic tool for patients with FL.