Previously posted around Tisha b'av 2009, then reposted March 6, 2011, on Nishmablog.
The following outline lists some of the parallels, primarily liturgical, between Purim and the 9th of Av.
1 Maariv - Nighttime A. Only Megillos that are read at night. - Eicho - Esther B. Similar Structure with Kaddish Tiskabel and v'Ato Kodosh 2 Shacharis - Omissions A. Purim - A "miracle" Holiday , no Hallel (Megilloh instead) B. 9th of Av - A Fast Day without - Selichos (Kinnos instead) - Tachanun & Ovinu Malkeinu 3 Shacharis - Chazoros Hashatz A. Only weekday repetitions of the Amido having Krovos/Krovatz
at least in the common Ashkenaz / Yekke Litrugy 4 Preceding Shabbos A. Purim preceded by Zachor B. 9th of Av preceded by Chazon 5 The Tanach's Pattern - Special Torah and Haftoro readings are read on the Shabbos
before the event, with the corresponding Megilloh on the day of the event. A. Purim - The Amalek Connection - Torah- Zachor - Navi - Haftoro of Zachor (Shaul's War with Amalek in Shmuel) - Kesuvim Esther B. 9 Av - The Eicho Connection - Torah - Eicho in Devorim - Navi - Eicho in the Haftoro of Chazon (Yeshaya) - Kesuvim - Eicho 6. Month-wide A. Mishenichnos Adar Marbin b'Simcho B. Mishenichnos Av M'maatin b'Simcho 7. Miscellaneous A. Some Pesukim in Esther are read to Eicho's melody (in particular Asher Heglo) B. Chiyuv S'eudo vs. Chiyuv Taanis C. Similar Minhogim not to work