I am conducting a research on the Intra-Middle East overall trade volume. For this, I gathered export and import data between GCC countries. However, export and import data do not match, i.e. UAE exports to Saudi Arabia are very far from Saudi Arabia imports from UAE. Am I mistaken or should't they be in the same ballpark area? The differences are so significant that they cannot be a result of currency conversions, etc.

 I would appreciate an answer.

This is difficult issue. The trade data discrepancies can be explained but need further research. There is an example of reconciliation study between Canada - USA  - Mexico on Compilers Manuals (http://comtrade.un.org/kb/attachments/SeriesF87-GUIDa64a82f464df46f69987ce41855c6cd1.pdf).

For your specific case, in general, country focuses more into Import (due to security, duties, control). Therefore, try to look into import data because generally it has better quality than export.