A longitudinal study with 400 patients diagnosed with myocardial infarction (MI) was conducted at the Cardiology department at Malmö University hospital in Sweden, between 2002 and 2005. The aim of the project was to identify personality and psychosocial factors, influencing patients’ actions and the prognoses after MI. The five factor model of personality, (measures on Neuroticism, Extraversion, Openness, Agreeableness, and Conscientiousness), coping strategies, depressive symptoms, the impact on delay seeking emergency care, smoking habits and cardiac health care utilization were studied. This thesis reports the result from four papers. In paper I the aim was to investigate whether maladaptive behaviour in the serial Color Word Test (CWT) alone or in combination with any specific personality dimensions were associated with severity of the MI. The indicators of severity of disease were maximum levels above median of the cardiac biomarkers troponin I and creatine-kinase-MB (CKMB), Q-wave infarctions, and a left ventricular ejection fraction (LVEF). The findings showed that maladaptive behaviour in combination with low scores on extraversion was associated with higher levels in cardiac biomarkers, following an MI. Another crucial factor for the prognoses and survival after a MI is early arrival to the emergency department and rapid intervention. In paper II we analysed the correlation of personality and psychosocial factors, with the time lag between the onset of coronary symptoms and seeking emergency hospital care. There was no significant conjunction in time delay and personality factors, coping strategies and depression. In paper III we examined whether personality traits, coping strategies and symptoms of depression were related to smoking cessation after an MI. Out of the 149 patients who smoked at baseline, 2 years follow-up data was available on 133 individuals, of these 44% (n=59) still smoked and 56% (n=74) had stopped smoking during the 2 years. Those who still smoked had lower score in the personality factor agreeableness, more lived alone and were unemployed in contrast to those who had stopped smoking. They also had significantly higher coping scores as confrontational behaviour. Finally, in paper IV we examined whether personality factors and depressive symptoms predicted cardiac health care utilization over the first two years after the MI event. Those MI patients showing traits of Neuroticism at baseline had significantly higher utilization at the out-patient cardiac clinic than those without. Individuals with a high score of depressive symptoms at baseline had instead a higher utilization of social workers and telephone contacts over the two year follow-up. In conclusion, we found that the personality factors extraversion, agreeableness and neuroticism were factors that had impact on MI severity, smoking cessation and out-patient clinic contacts, while delay in seeking acute care was not affected by personality factors, depression or coping strategies. Maladaptive behaviour and a confronting coping strategy influenced MI severity and smoking cessation 2 years after an MI. Taking personality factors and coping strategies more into consideration when caring for patients in cardiac rehabilitation might be indicated.