Abstract Background Time-spatial labeling inversion pulse (Time-SLIP) magnetic resonance imaging allows non-invasive visualization of cerebrospinal fluid (CSF) movement. Our study evaluated the sensitivity of the Time-SLIP tag placement on the measurement of CSF reflux from the third ventricle into the lateral ventricles via the foramen of Monro. Findings Multiple Time-SLIP MRI scans were obtained in three healthy volunteers (23–55 years of age) evaluating the observed CSF pulsation and reflux from the third ventricle into the lateral ventricles while varying the placement of the tag. Linear regression was performed to evaluate the effects of tag position on the amount of visualized reflux and pulsation. Variation in the position of the tag relative to the plane of the free margin of the septum pellucidum produced a significant inverse variation in the observed reflux into the lateral ventricles (R 2 = 0.74). The further the distance of the top (superior edge) of the tag from the plane of the free margin of the septum pellucidum, the less reflux into the lateral ventricles was observed ( P = 0.006). Conclusions The amount of observed CSF reflux into the lateral ventricles in Time-SLIP MR imaging is dependent on the positioning of the CSF tag with decreasing amount of visualized reflux the further caudal the CSF tag is relative to the free margin of the septum pellucidum.