In 2-D Mammography, breast tissues are superimposed in single projection image thereby possibly masking small cancer. X-ray breast tomosynthesis (XBT) is a technique for reducing this problem by providing a 3-D image. However, it still provides only anatomic (structural) information. Since cancerous and harmless breast masses (lesions) often have similar structures, distinguishing them using structural imaging alone is difficult. The task of distinguishing between benign and malignant breast lesions can be significantly aided by taking advantage of the differences in their biological (functional) characteristics. Molecular breast imaging (MBI) is a recent technique that uses intravenously injected compounds (tracers) that are taken up to a much greater degree by malignant lesions than benign ones. By attaching a radioisotope atom to these tracer molecules they can give off a signal that can be detected by specially designed cameras placed near the breast. These cameras permit functional imaging of the entire breast and have resulted in reliable detection of tumors less than 1 cm in size. Nevertheless, similar to Mammography, the 2-D nature of MBI prevents any depth information of lesions from being obtainable. Moreover, the correction for gamma signal attenuation through the breast is virtually impossible in MBI. Our group is developing a unique dual modality tomographic (DMT) breast scanner that combines x-ray tomosynthesis and 3-D MBI tomosynthesis (MBIT) on a single integrated gantry. This talk will focus on the functional part. Specifically, image acquisition, reconstruction and restoration in MBIT will be covered.