The concept of secondary traumatic stress refers to a process whereby "an individual who observes the suffering of another, parallel experience the same emotional responses to actual or anticipated emotions of another person," Moreno, Morante, Rodriguez & Garrosa (2004). Based in this model Moreno, Garrosa, Morante, Rodriguez & Losada (2004b) designed the Secondary Traumatic Stress Questionnaire (STSQ). This study presents a comparative study of secondary traumatic stress realized with 427 subjects divided in two samples of firefighters and emergency paramedics. Emergency paramedics perceived more social pressure and a higher level of comprehension, while firefighters had a higher perception of work overload, high level of empathy and social consequences. Gender differences show that women perceived more social pressure at work and men perceived more overload and sense of humor. Correlations between the subscales of STSQ, confirm the relationship between the dimensions of the process model developed by Moreno, Morante, Rodriguez & Rodriguez (2008).