She is the same height and build as her brother, which is reasonably short and slight, although not abnormally so. She has blonde hair, cut just above her shoulders (and slightly shorter later in the series) and pale blue eyes.
Krillin is very attracted to her looks, even though she is heartless and determined to kill the Z Fighters. He refuses to activate a self-destruction mechanism on her, which would have prevented Android Cell attaining 'perfection' by absorbing her and her brother.
After Cell is defeated, Krillin wishes for Android 18 to be turned into a human. This is, however, not within the Dragon's power.
Nonetheless, Krillin and Android 18 eventually have a child together, a daughter Marron.
Android 18 is paired with Mr Satan (Hercule) in a championship fight. She does not want the fame and attention of winning, so allows Hercule to beat her provide he pays her the prize money.