Regional Differences in Poland
Regional Differences in Poland although still visible are not that big like they used to be. Much of the division in terms of economy, population, and cultural aspects are based in the period of Polish partitions and the shift of borders after WWII. The main division is between the western part of Poland and the eastern part of Poland. And like previously mentioned they are the result of 123 years of partitions between German Empire, Austro-Hungarian Empire and Russian Empire. If you look at any map that shows infrastructure density, dialects of a language or any other aspect that can be an effect of the population distribution and influence of neighbor countries you are doomed to see the borders appear as they were.
Polish Borders over time
In order to understand any division, you have to familiarize yourself with previous polish borders. Please keep them in mind.
Partitions of Between German Emire, Austro-Hungarian Empire, Russian Empire the end of XVII century:
Second Polish Republic 1918-1939
And now for the divisions. Because of Russian influence or occupation, eastern territories of Poland has always been substantially poorer than the western or they have lagged behind in many ways. Let us take a look at the railroad density chart that clearly shows that on the previously German Partition territories the local roads density is much higher than in the Second Republic.
On this image, you can clearly see the previous borders showing the partitions between Russia, Germany, and Austro-Hungary. People in east Poland have a more conservative approach to the question of how a country should be run.
Again. You can clearly see the partitions of Poland.
If you look at the map of privately owned woods you can clearly see the border of the second republic. This shows that in these areas people have a more capitalist mentality in terms of how you can profit from land ownership. So not everything that was influenced by Germany was good. Poles on their own knew how to manage the resources.
How big are the differences
The actually is not that big. These examples above might be interesting but Poland is actually a very unified country with a similar mentality and mode of operating all over the place. Sure salaries are a bit higher in the west than in the east. Ans sure they are waaaaay higher in big cities, but overall unification of the country is very good. So the Regional Differences in Poland should not be a concern for you if you think about coming here for business or pleasure.