The blind regions for single-borehole bistatic and monostatic pulse radars are considered in this paper. The blind region of a single-borehole radar may restrict its capability on detecting anomalies adjacent to the antenna. We explain the causes of the blind regions in bistatic and monostatic radars. In bistatic radar, the blind region is caused by direct signal along the borehole. In contrast, the blind region of monostatic radar is complexly generated by direct signal radiated from the circuit, feed reflection and switching noise. And we investigate how much such critical signals decrease using switch time delay. The blind region of a single-borehole pulse radar is measured using practical experiments. And the considerations of the blind region according to the switching time for monostatic radar system are also analyzed. Finally, we demonstrate B-scan data of actual adjacent target with optimum blind region.