I was thinking the same as SarahJane. It's got like different ingredients in it. But until you try it or hear from someone else who has tried it, you'll never know. If it were me I'd try it!!! I love experimenting 
Lazy_Susan 
What are you trying to make? Cake or icing...If you are making Choco buttercream you an use semisweet chocolate 1 oz pieces...
Well, I would say no because your pudding powder is made up of many things, mostly sugar, so you are going to have to use a whole lot of pudding powder to make the equivalent of the chocolate flavouring of cocoa powder plus the sugar would require adjustment and the other ingredients in the pudding powder will likely mess up the ratios in your recipe.
However is you have chocolate chips or baking chocolate, there are ways of substituting one for the other but they also require adjustments for sugar and fat.
What other kinds of chocolate do you have on hand and what are you trying to make? I could suggest some equivalents for you.
Hugs Squirrelly
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