In 124 primary breast cancer patients the maximum values of the lateralisation of the internal mammary chain (IMC) and their corresponding depths could be determined by scintigraphy and ultrasonography in 77% and 85% of the cases, respectively. With respect to the lateralisation it appeared that these values were uncorrelated between the two methods. With respect to depth correlation was found (correlation coefficient 0.34; P=0.001). We conclude that substantial differences are noted. Irradiation of the IMC based on computed tomography treatment planning might be a better alternative.