The objective of this thesis is to develop an understanding and performance evaluation of plastic packages for surface mount devices. Of particular interest in this work are packages for use in the gigahertz range. In order to accurately model these packages, time and frequency domain measurements of two different packaged structures are performed. Equivalent electrical circuit models for the structures are then derived and compared with measured results to determine quality of fit and validity of these models. With this modeling technique, various package parasitics affecting the circuit performance can be evaluated and compensated for in the electrical equivalent models.