We report a new usage of folic acid-modified dendrimer-entrapped gold nanoparticles (Au DENPs-FA) as nanoprobes for in vitro and in vivo targeted computed tomography (CT) imaging of human lung adencarcinoma. In this study, Au DENPs prepared using amine-terminated generation 5 poly(amidoamine) dendrimers as templates were covalently linked with FA, followed by an acetylation reaction to neutralize the remaining dendrimer surface amines. The formed Au DENPs-FA was used for both in vitro and in vivo targeted CT imaging of human lung adencarcinoma cells (SPC-A1 cells) and the xenograft tumor model, which express folic acid receptors (FAR) verified by immunohistochemical staining. MicroCT images show that SPC-A1 cells can be detected under X-ray after incubation with the Au DENPs-FA in vitro and the xenograft tumor model can be imaged after intravenous, intratumoral, and intraperitoneal administration of the particles. Transmission electron microscopy data confirm that the Au DENPs-FA is able to be uptaken dominantly in the lysosomes of the cells. Combined morphological observation of cells after Hematoxylin and Eosin staining, MTT (3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide) assay of cell viability, and flow cytometric analysis of cell cycle and apoptosis show that the Au DENPs-FA does not affect cell morphology, viability, and cell cycle and apoptosis, indicating their good biocompatibility at the given concentration range. These findings suggest that the developed Au DENPs-FA have a great potential to be used as imaging probes for targeted CT imaging of human lung adencarcinoma.