Children's hospitalisation is difficult for the family and the immediate environment. In these cases, the provision of psychological support is particularly important. Chronically ill children who are regularly hospitalised are in a particularly difficult situation, often feeling vulnerable. Our research aims to explore and analyse in detail the psychological state, attitudes and mental health of chronically ill children and to compare patient groups (children receiving care in pulmonology, gastroenterology, onco-haematology and rehabilitation) to understand the interacting factors, which may be of great importance for quality patient care and for measures to improve patient care in the future. We studied chronically ill children (N = 107) aged 10 to 18 years (M = 14.3; SD = 2.0), cared for by the Department of Paediatric Rehabilitation, Paediatric Psychiatry and Psychosomatics of the University of Debrecen Clinical Centre, the second largest paediatric institution in Hungary. In our survey, sociodemographic questions, the Connor–Davidson Resilience Scale, the Satisfaction With Life Scale, the Cantril Ladder, the Non-Productive Thoughts Questionnaire, the Problematic Internet Use Questionnaire, the Drawing version of Pictorial Representation of Illness Self-Measure (PRISM-D), the Beck Depression Inventory—Shortened Scale, the Illness Intrusiveness Ratings Scale, the Spielberger State-Trait Anxiety Questionnaire—Child Version and the Strength and Difficulty Questionnaire were applied. One-way analysis of variance (ANOVA) was used to examine differences between groups, and Pearson rank correlation analysis was used to measure the relationships between individual variables. The results show significant differences between patient groups in terms of resilience, depression, nonproductive thoughts, problematic internet use, anxiety and coping, but no consistent pattern in the development of scores. In addition, for some psychological correlates, the role of sociodemographic background also showed significant results. The practical utility of our study is that using questionnaire methods to map patient satisfaction, compliance, and patient attitudes will provide regarding the factors that influence the mental health status of children living with chronic illnesses. In the light of this, additional methods and tools can be included to improve the quality of healthcare and to develop a set of procedures that will serve the intended purpose.