# Should PCA be (always) done before Naive Bayes classification

For general cases, I don't think doing PCA first will improve the classification results for the Naive Bayes classifier. Naive Bayes assumes the features are conditional independent, which means given the class, $$p(x_i|C_k)=p(x_{i}|x_{i+1}...x_n,C_k)$$, this does not mean that the features have to be independent.