The present study investigated the additive, synergistic, and moderating effects of job demands and job resources on well-being (burnout and work engagement) and organizational outcomes, as specified by the Job Demands-Resources (JD-R) model. A survey was conducted among two Chinese samples: 625 blue collar workers and 761 health professionals. A series of multi-group structural equation modeling analyses supported the two processes proposed by the JD-R model: (1) the stress process that originates from job demands and leads, via burnout, to negative organizational outcomes (turnover intention and low organization commitment); and (2) the motivational process that originates from job resources and leads, via work engagement, to positive organizational outcomes. In contrast to moderating effects, synergistic effects of job demands and job resources on burnout and work engagement were found in both samples. However, after controlling for additive effects of job demands and job resources, these synergistic effects largely disappeared. In conclusion, the hypothesized additive effects of the JD-R model were found but the evidence for additional synergistic and moderating effects was weak. (Contains 4 tables and 3 figures.)