The more recent focus on the link between HRM practice and organisational systems has been on the potential benefits of mutuality in employment relationships. The key to this notion of mutuality is the connection between worker well-being and performance. Although a common area of study for psychology, this relationship has received limited attention from HRM scholars. However, these initial endeavours have raised some concerns about measurement. First, there appears little consensus about which particular facet of well-being is most crucial to determining performance and, second, concern has been expressed over the validity of the different approaches taken to assessing performance. Our study addresses these issues by exploring the relationships between three different measures of well-being and two different measures of performance amongst a student cohort. Results show that life satisfaction shares a significant, positive relationship with objective performance ratings, while attentiveness, a facet of positive affect, shares a significant positive relationship with subjective performance. We explore the reasons why these different facets of well-being might be related to our different performance assessments and then, in giving consideration to these findings, discuss their implications for the measurement of well-being and of performance in workplace studies.