Cells may be somatic or gametic.
Somatic cells are those that form the body of an organism, and are diploid (contain 2 pairs of chromosomes). As they do not give rise to future organisms, radiation to somatic cells may lead to long term effects in that person only. Some somatic cells are relatively radioresistant (neurones, muscle cells).
A gametic cell is haploid, involved in reproduction, and fuses with its opposite type to form a diploid cell. Gametic cells arise through meiosis, where the cell divides to form two daughter cells, which then also divide to give rise to four haploid daughter cells. If gametic cells are irradiated and suffer damage, long term effects are unlikely to effect the person (aside from potential infertility) but may effect their children due to mutations in the genetic code of the gamete.
Gametes tend to be significantly more radiosensitive than most somatic cells.