Scalar spatial correlations in the supersonic mixing flowfield produced by a sonic transverse injection of air into a Mach 2.0 supersonic airstream were investigated using acetone planar laser-induced fluorescence (acetone PLIF) data. Side-view and end-view images were obtained in several planes to characterize the turbulent structure and three-dimensionality of the mixing flowfield. Single-time two-point spatial correlations of injectant concentration were obtained from the acetone PLIF data. Contour maps of the correlations indicated an organized large-scale structure in the upper region of the jet. Side-view correlation maps revealed that the shape of the large dominating structure was elliptic, and that its major axis turned from backward-leaning to forward-leaning as the reference point of correlation moved downstream. End-view correlation maps revealed that the instantaneous jet plume appeared by turns either in the top or in the lower sides of the timeaveraged injectant plume in each cross-section.