Primary immunodeficiency disorders (PID) are a group of heterogeneous disorders characterized by recurrent infections, autoimmunity, increased lymphoproliferative disorders and other malignancies. PID is classified into cellular or humoral disorders or a combination of both. We evaluated the clinical differences among adult patients with three variants of PID: common variable immunodeficiency (CVID), idiopathic CD4 lymphopenia (ICL) and combined immunodeficiency (CID). We retrospectively compared demographics, immunological characteristics, clinical presentations and outcomes of CVID, CID and ICL patients followed from 2012 to 2018. In our cohort, we identified 44 adult patients diagnosed with CVID (22), CID (11) and ICL (11). Malignancy was associated with CID, as seven of 11 patients in this group were diagnosed with malignancy compared to CVID (three of 22) or ICL (two of 11) (P = 0•002 and 0•03, respectively). Malignancies were also linked to male gender [odds ratio (OR) = 5, 95% confidence interval (CI) = 1•12-22•18) P = 0•0342] and a low ratio of CD4/CD8 < 0•8 (OR = 5•1, 95% CI = 1•22-21•28, P = 0•025). Among CID and ICL, two of 11 patients died in each group, while no death was documented among CVID group (P = 0•04). Autoimmune manifestations did not differ between groups. Similarly, the rate of infections was similar between groups, although infectious agents vary. CID is associated with a high risk of malignancy compare to CVID or ICL. Among adults with PID, male gender, low CD4 and a CD4/CD8 ratio of < 0•8 may serve as risk factors of concomitant malignancy. Surveillance of lymphocyte subpopulations should be considered for all adults.