Purpose: To study the relationship between the DNA content of human chromosomes and their involvement in radiation-induced structural chromosome aberrations. Material and methods: Human lymphocytes were cultured after exposure to 5 Gy of X-rays. FISH-painting was performed for all human chromosomes. Results: The results indicate that with the exception of chromosome 20, there was a good fit between the DNA content and the number of exchange-type aberrations and the number of breaks. However, there was a significant tendency for short chromosomes to be more affected than expected and for long chromosomes to be less affected than expected. A better fit was observed when, instead of DNA content, the surface area of the chromosome territories obtained from a spherical model was taken into consideration. Conclusions: The tendency for short chromosomes to be more involved and long chromosomes to be less involved in exchange-type aberrations could be related not only to their DNA content but also to their interphase territory surface area.