The P300 component of the ERP has often been suggested as a viable alternative to skin conductance response (SCR) in a concealed information test (CIT). Little is known, however, about the association between these two measures. In a mock crime study we simultaneously recorded skin conductance response (SCR) and midline EEG, while stimuli were presented with a short inter stimulus interval. Overlap between SCRs to successive stimuli was handled by presenting stimuli in a specially balanced order using M-sequences (Buracas and Boynton, 2002). SCRs were smaller than typical, but differed between crime relevant and crime irrelevant stimuli, as did P300. Most importantly, SCR and P300 were uncorrelated, indicating that different mechanisms underlie these measures in a CIT.