Keloids and hypertrophic scars are different forms of excessive dermal fibrosis thought to be caused by regulation of cellularity increase and decrease during the wound-healing process in predisposed individuals. Differences between keloids and hypertrophic scars include distinct clinical features, histologic evidence, and cellular function in response to molecular events. Keloids and hypertrophic scars are the results of increased fibroblast density and extracellular matrix substances. Interactions between epidermal keratinocytes and dermal fibroblasts play an important role in regulating tissue homeostasis and processing scar formation. Keloids and hypertrophic scars are the two different stages of the same process that is based on separate clinical and histochemical entities. The aim of this review is to provide updated information regarding similarities and differences between keloids and hypertrophic scars as two different sides of the same coin. This article will also enable the dermatologist to better understand fundamental biology of the scarring.