Polymeric micelle of the A3B-type lactosome comprising (poly(sarcosine))3-b-poly(l-lactic acid) was labeled with 111In. The 111In-labeled A3B-type lactosome was administered to the model mice bearing meningeal dissemination and bone metastasis at mandible. With single-photon emission computed tomography (SPECT) imaging, the meningeal dissemination was identified successfully by 111In-labeled A3B-type lactosome, which was superior to 201TlCl in regard of the imaging contrast. The 111In-labeled A3B-type lactosome was also potential in imaging selectively of bone metastasis at mandible, whilst a nonspecific imaging of the whole bone was obtained by the SPECT imaging using 99mTc-HMDP. The polymeric micelle of the A3B-type lactosome was therefore found to be effective as a vehicle of 111In to be targeted to meningeal dissemination and bone metastasis.