To determine dining out behaviours of fast foods at five different fast food restaurants of Youido apartment compound in Seoul, a survey was conducted of 460 customers ranging in age from 7 to 29 year, from October 1 to 5th, 1986. Findings are summarized follows: The reasons the customers the fast food restaurants by the highest percentage were the following in the order: 'the atmosphere in which fast food is eaten is enjoyable for the companionship', 'convenient to dining', 'the surroundings and dining equipment are pleasant and hygienic', and 'to be able to stay as long as I want'. The majority of the customers visited the fast food restaurants with their friends between 1pm and 5pm. The fast foods purchased by the customers were mostly for snack rather than a full meal. Preference was a major factor in food selection from available meun items. Ice cream, Kentucky fried chicken, rolled rice with laver I rice cake stew, fried Mandoo were ranged high on the list of liked foods, in contrast, lower preference was for noodle soup, small red bean porridge, pinenut porridge, and persimmon punch.