Japanese Wikipedia tries to clarify the difference.
日本ではよく、チヂミと「パジョン」（파전）が混同されることがあるが、パジョンとはプチムゲ（慶尚道ではチヂミ）の一種である「ジョン」（전）のうち、ネギ（パ、파）を使用したものである。「ジョン」にはこのほか、キムチを使用した「キムチジョン」（김치전）、ジャガイモを使用した「カムジャジョン」（감자전）、海産物を使用した「ヘムルジョン」（해물전）などがある。My rough translation follows (as amended by Matt of No-Sword), using Japanese ro
In Japan, chijimi and pajon (파전) are often confused, but pajon is actually jon (전) that uses green onions (pa, 파). Jon, in turn, is a type of puchimuge (called chijimi in Kyongsang Province). There are other types of jon that use kimchee (kimuchijon, 김치전), potato (kamujajon, 감자전), or seafood (hemurujon, 해물전).While doing a bit of nostalgia-driven culinary fieldwork near the Sannomiya area of Kobe (where I went to high school), I chanced upon a menu that listed both pajon and chijimi side by side (pictured above). So I sampled a small order of pajon to go with a glass of Taishikan Weizen at the Tor Road branch of the New Muenchen Kobe Taishikan, a beer hall whose ambience I fondly remembered, but whose location had drifted away from me (unless it was rebuilt in a different location after the Great Hanshin Earthquake of 1995).
My research results seem to indicate that Kyongsang-style chijimi more closely resembles Osaka-style Japanese okonomiyaki than does pajon, because that style of chijimi has both a thicker batter and a milder dipping sauce. If chijimi is ever served with mayonnaise, well, that would add an even more decisive factor. The essential difference seems to lie in the batter. Jon uses a lighter egg batter for quick frying, while chijimi uses a heavier batter thickened with more flour. The チヂミ粉 'chijimi flour' that you can buy in Japanese supermarkets apparently contains bean flour as a thickener.
PS: In my careful scrutiny of the New Muenchen Tor Road menu, I noticed a few odd transcriptions out of Japanese katakana into something other than German, Italian, or English: waizen beer, focatcha bread, and humberger sandwich. Being the roving editorial dogooder that I am, I wrote out a note for the management listing the oddities and suggesting corrections. The Japanese spellings in my note were no less idiosyncratic than the romanized spellings on the menu, but I hope the management at least will get a second opinion on the items I noted. (The menu at the main brewpub was much more accurate. It also featured beer-flavored ice cream, which was fortunately beyond the scope of my fieldwork agenda.)
eGullet Forum has a pertinent discussion thread on Korean food in Japan. Some commenters clearly regard Chijimi as just a dialectal synonym of Pa Jun.
UPDATE: I've made some revisions in response to corrections by Matt of No-Sword, who was kind enough to be my roving editorial dogooder.