A Bonse–Hart ultrasmall angle x‐ray scattering (USAXS) instrument employing both synchrotron and conventional x‐ray sources was constructed. The instrument could be used to determine the structure of systems with inhomogeneity sizes on the order of ∼1000 nm. The characteristics of the instrument by using synchrotron and conventional x‐ray sources were compared. The use of synchrotron radiation showed much improved features not only in scattered intensity, but also in angular resolution. The scattered intensity was increased by a factor of about 20. Therefore weaker scattering systems could be investigated. By using the synchrotron radiation, the deficiency of the Bonse–Hart camera could be compensated. An angular scan containing ∼30 data points in the scattering angle region smaller than ∼2 mrad with reasonable signal‐to‐noise ratio could be completed within 5–10 min for samples with reasonable scattering power. Therefore, kinetic studies could be possible if the half time of structural development in a system is of the order of hours. For static experiments, a conventional x‐ray source could be used more conveniently to obtain a scattering curve with similar quality as that by means of synchrotron radiation partially because the channel‐cut crystals were not optimized for the synchrotron beam divergence and partially because alignments could be accomplished at a more leisurely pace using the conventional x‐ray source.