Objective: To study the reasons for first-line nurse managers to resign, their perceptions of difficult situations, experience of support and satisfaction with work. Background The intentions of first-line nurse managers' to stay at their posts varied between 45% and 75% in different studies. Methods: Data were collected by questionnaire and letters from 32 first-line nurse managers who had left their posts. Qualitative content analysis was used to analyse the letters. Results: Eleven first-line nurse managers resigned due to reorganization or other changes and 19 due to their own accord. Reasons to leave were personal, organizational, as well as lack of support from and relations to the head of department. Difficult situations were unclear conditions, lack of support from supervisors and, implementation of changes, staff matters and economy. Important support was personal, organizational, practical and to have opportunities for development and education. The perception of work satisfaction was higher after resignation. Conclusions: The dominant reason to leave was reorganization and other changes. The relation to the head of department influenced the first-line nurse managers' overall work situation.