Abstract <p>The effect of long-term exposure of solutions on the growth characteristics of anthracene crystals has been studied. It is established that long-term (&gt;3 weeks) exposure of saturated solutions in air causes their aging with subsequent precipitation of accompanying yellow needle-shaped crystals, along with anthracene crystals. Using single-crystal X-ray diffraction, it was found that the accompanying needle-shaped crystals have a structure described by the sp. gr. <i>P</i>2₁/<i>c</i> (<i>Z</i> = 4) and consist of 9,10-anthraquinone molecules. The formation of solid solutions based on anthracene and 9,10-anthraquinone molecules during their joint crystallization was not revealed. It is shown that the observed red shift of the fluorescence spectrum of crystals, which occurs when using some commercially available grades of anthracene for growth from a solution, is due to the presence of a homologous impurity (tetracene) in the starting material. The crystal-chemical aspects of incorporation of impurity molecules into the anthracene crystal structure are discussed.</p>