The invention discloses a photographing optical lens assembly, an image capturing unit and an electronic device. The photographing optical lens assembly includes lens elements including, in order from an object to an image side, a first lens group, a second lens group and a third lens group. The first lens group includes a first lens element and a second lens element. The second lens group includes a third lens element, a fourth lens element and a fifth lens element. The third lens group includes a sixth lens element, a seventh lens element and an eighth lens element. The first lens element has positive refractive power. The seventh lens element has an object-side surface and an image-side surface being both aspheric. The eighth lens element has an image-side surface being concave in a paraxial region thereof, wherein both an object-side surface and the image-side surface thereof are aspheric, and the image-side surface of the eighth lens element has at least one reflection point. An air gap in a paraxial region is located between every two lens elements of the photographing optical lens system that are adjacent to each other. The invention also discloses an image capturing device comprising the image capturing lens groups and an electronic device comprising the image capturing device.