Background:
Clinical psychologists are observing an increasing number of children with comorbid disorders such as autism spectrum dis-order (ASD), attention-deficit/hyperactivity disorder (ADHD), anxiety disorders, depressive disorders and others. Due to the importance of higher efficacy of implementing early therapeutic interventions, factors determining the age of first diagnos-tic intervention and the age of diagnosis are particularly significant aspects when considering this topic.

Participants and procedure:
An in-depth analysis of the documentation of 112 patients of one of the psychological and pedagogical counselling centres was conducted to identify family and developmental factors that contribute to the diagnostic decision-making process in children with comorbid disorders. These children were 2-17 years old and diagnosed with co-occurrence of ASD and other disorders.

Results:
The results indicate that children with comorbid disorders are reported for diagnostic intervention at the age of 4 years old and 3 months old (M = 4.24, SD = 2.29) and the mean age of receiving an ASD diagnosis is 7 years old and 3 months old (M = 7.28, SD = 3.25). Predictors of the age of diagnostic intervention and ASD diagnosis were also identified. Somatic dis-eases and potentially speech disorders were related to the earlier age of diagnostic intervention, whereas learning difficul-ties were related to the later age of diagnostic intervention. Moreover, it has been found that children with comorbid ex-ternalizing disorders have an earlier age of diagnostic intervention than children without disrupting behaviours. However, this circumstance does not affect the age of ASD diagnosis.

Conclusions:
It is important to raise parents’ awareness of detecting early markers of disorders as intervention and diagnosis are imple-mented too late. In such circumstances, therapeutic interventions under-taken may have limited effectiveness.