A brain-computer interface has received a lot of attention for years, because this interface can be a useful tool for locked-in patients such as amyotrophic lateral sclerosis (ALS) patients. If the placement of the electroencephalogram (EEG) electrode becomes easier to attach, this interface will be more practical and become widely used among people including healthy individuals. In this research, we have focused on the forehead position called F_<p2>, and examined if the event-related potentials can be detected at this position. Comparing to the signal at the commonly-used occipital position O_z, the signal level at F_<p2> is evaluated with two proposed methods. Experimental results reveals that some subject has high accuracy at however, variance is quite large. Therefore, it is hard to draw a conclusion the signal level is better than the one at O_z. Using second evaluation method, one subject's accuracy at F_<p2> is nine times larger than others.