Plastic surgery must achieve the best cosmetic results, and it helps to consider certain skin lines. Aging and scars can cause the face to become lined, and we have noticed various facial lines among patients or their relations who have come to our outpatient clinic. These lines are sometimes single and there are sometimes 2–3 parallel lines generally in the same area of the face, such as the lateral orbital, temporal, frontal, and buccal regions. After detailed evaluation, we concluded that these oblique or horizontal wrinkles were caused by the position in which they slept. All of them slept prone, with their faces buried in the pillow, which over many years has caused wrinkling of the skin. We think therefore that sleeping position should be considered as an aetiological factor in the formation of wrinkles. The lines that should be taken into consideration during operation are Langer's lines, or relaxed skin tension lines, but not sleep lines. Here we describe the possible aetiology of sleep lines on the face.