The aim of this study was to validate the Dutch version of the Kessler-10 (K10) as well as an extended version (EK10) in screening for depressive and anxiety disorders in primary care. Data are from 1607 participants (18 through 65 years, 68.8% female) of the Netherlands Study of Depression and Anxiety (NESDA), recruited from 65 general practitioners. Participants completed the K10, extended with five additional questions focusing on core anxiety symptoms, and were evaluated with the WHO Composite International Diagnostic Interview (CIDI lifetime version 2.1) to assess DSM-IV disorders (major depressive disorder, dysthymia, generalized anxiety disorder, social phobia, panic disorder, agoraphobia). Reliability (Cronbach's α) of the Dutch K10 was 0.94. Based on Receiver Operating Characteristics (ROC) analysis, the area under the curve (AUC) for the K10 for any depressive and/or anxiety disorder was found to be 0.87. The extended questions on the EK10 significantly improved the detection of anxiety disorders in particular. With a cut-off point of 20, the K10 reached a sensitivity of 0.80 and a specificity of 0.81 for any depressive and/or anxiety disorder. For the EK10, a cut-off point of 20 and/or at least one positive answer on the additional questions provided a sensitivity of 0.90 and a specificity of 0.75 for detecting any depressive and/or anxiety disorder. The Dutch version of the K10 is appropriate for screening depressive disorders in primary care, while the EK10 is preferred in screening for both depressive and anxiety disorders.