[en] By answering simple questions, this document proposes a brief overview of radiographic and scanner-based examinations. It recalls that these both techniques use X rays, the cumulative dose of which could slightly increase a risk of cancer on a long term. It outlines that the benefits of these examinations are much more important that the related risks. It indicates the received dose (compared to a daily natural irradiation) for different kinds of examination and for different parts of the human body. It outlines the sensitivity of children to X rays, gives some recommendations regarding these examinations (they are not automatic; the doctor must explain why he chooses them, previous examinations and photos must be kept and brought with; the received dose must be specified in the examination report)