The use of Zorn ZFG-3000 portable Lightweight Deflectometer (LWD) in the in-situ assessment of pavement quality was investigated in this research. A lower load and a shorter load pulse duration are used in a LWD as compared to a Falling Weight Deflectometer (FWD). LWDs are ideally suited for the structural evaluation of a single pavement layer at a time. LWDs could serve as a cost effective, non-destructive, in-situ test method for the evaluation of the mechanistic properties of the pavement and help to bridge the gap between the design and the construction of the pavements. The performance of the Zorn ZFG3000 LWD device in measuring the stiffness of asphalt layer was studied during construction of full-depth asphalt pavements. While it was observed that the Zorn ZFG-3000 LWD was easy to use and able to determine the general trends in increasing/decreasing stiffness of the asphalt pavement layer, the researchers found very little correlation between the LWD measured modulus and the density of the asphalt mat at the test locations as determined from roadway cores. Further, very little correlation was observed between the LWD measured modulus and the dynamic modulus of the pavement at the test locations. The LWD measurements also did not appear to depend on any pavement parameters such as mix type and gradation, lift thickness, total asphalt pavement thickness, and type of construction. Based on these findings, it is concluded that the Zorn ZFC-3000 LWD is not suitable for measuring the stiffness of asphalt pavements and for use in Quality Assurance of pavements.