While doing research about Articulation Disorders, I began to see Phonological Disorders pop up and wondered what the difference was. The article I found focused on that very question. An articulation disorder occurs when a child (or adult) have trouble making individual speech sounds. A phonological disorder results from a difficulty in organizing speech sounds, this occurs at the cognitive level. Despite affecting different aspects of speech, it is possible for an individual to have both disorders.
Bowen, C. (2002). The difference between an articulation disorder and a phonological disorder. Retrieved from www.speech-language-therapy.com/phonetic_phonemic.htm on (Oct. 15). Referenced the Journal of Speech and Hearing Research, 36, 105-140.