It is important to measure how well Strategic Information Systems Planning (SISP) is done and how planning is improving over time. SISP measurement and assessment is associated with a huge amount of variables and interactions. SISP is confronted with two problems: a problem of comparing the importance of the tangible and intangible properties of its elements, measured by different scales, and a problem of synthesis of influence of these elements on the SISP constructs or the overall SISP success. The reported SISP measurement methods are not capable of overcoming these problems. This paper demonstrates a unique implementation of the Analytic thinking theory for establishing the relative and absolute importance of the SISP constructs. This theory is operationalized through the Analytic Network Process (ANP) and Analytic Hierarchy Process (AHP) methods which have capability to synthesize the various measures into a single overall measure of SISP maturity or SISP success. Based on AHP/ANP, the paper presents the framework for assessment and measurement of SISP maturity which is empirically validated in Australian environment.