Abstract Use of hyperpolarized noble gases with MRI/magnetic resonance spectroscopy (MRS) has been expected as a new technique for functional imaging. The noble gases ( 3He and 129Xe) polarized by optical pumping have enabled visualization of the lung gas space. We report the spectroscopy of the gas or dissolved phase of 129Xe in the lungs of mice. The effect of an intravenous injection of MRI contrast agent was examined in relation to the signal assignment, which was essential for the analysis of lung functions. After inhalation of hyperpolarized xenon gas, gas and dissolved phase signals of 129Xe were observed at 0–10 and 190–200 ppm, respectively, in the chests of mice. The dissolved phase signals decreased in intensity immediately after intravenous injection of Gd-DTPA. These signals were assigned to originate from plasma or interstitial space in the lung, considering the distribution of the contrast agent. Such a study would be useful for the diagnosis of lung function.