During the in vivo counting of individuals using a whole body counter at nuclear power plants (NPPs), external skin contamination is occasionally mistaken for internal radioactive contamination. This not only confuses the degree of external contamination and internal contamination, but can also result in the excessively conservative estimation of radioactive contamination. In this paper, previous experiments to improve in vivo counting at NPPs are introduced briefly and the practical application of techniques presented in those experiments to Korean NPPs is demonstrated in detail.