A quantum dot including a core comprising a first semiconductor nanocrystal including a zinc chalcogenide and a semiconductor nanocrystal shell disposed on the surface of the core and comprising zinc, selenium, and sulfur. The quantum dot does not comprise cadmium, emits blue light, and may exhibit a digital diffraction pattern obtained by a Fast Fourier Transform of a transmission electron microscopic image including a (100) facet of a zinc blende structure. In an X-ray diffraction spectrum of the quantum dot, a ratio of a defect peak area with respect to a peak area of a zinc blende crystal structure is less than about 0.8:1. A method of producing the quantum dot, and an electroluminescent device including the quantum dot are also disclosed.