The Subjective Wellbeing (SWB) literature is replete with competing theories detailing the mechanisms underlying the construction and maintenance of SWB. The current study aimed to compare and contrast two of these approaches: multiple discrepancies theory (MDT) and an affective-cognitive theory of SWB. MDT posits SWB to be the result of perceived discrepancies between multiple standards of comparison. By contrast, affective-cognitive theory asserts that SWB is primarily influenced by trait affect, and indirectly influenced by personality and cognition through trait affect. Participants comprised 387 individuals who responded to the 5th longitudinal survey of the Australian Unity Wellbeing Index. Results of Structural Equation Modelling (SEM) indicated the poorest fit to the data for the MDT model. The affective-cognitive model also did not provide a good fit to the data. A purely affective model provided the best fit to the data, was the most parsimonious, and explained 66% of variance in SWB.