Slavic honorifics

Speakers of Slavic languages and Lithuanians (Baltic languages) use two main sets of honorifics. West Slavs and Ukrainians use the title "Pan", South Slavs and Russians use "Gospodin", while Belarusians use either "Pan" or "Spadar", and Lithuanians use either "Ponas" or "Gaspadorius".
Usage of Pan.
"Pan" is used to varying degrees in a number of countries – Poland, the Czech Republic, Slovakia, Ukraine, Belarus and Lithuania ("Ponas"). Historically, "Pan" was equivalent to "Lord" or "Master" (ruler, suzerain).
"Pan" is most common in Poland. The feminine form is "Pani" and the collective is "Państwo". "Panna" is sometimes used to refer to young women but is becoming less common. The use of Pan differs significantly from English honorifics. It is used as an honorific (roughly equivalent to Mr) before the name (first name and surname, only surname, or only first name) and as a form of address without the name (roughly equivalent to "Sir").
Use of "Pan" with the first name in Poland marks a combination of familiarity and respect. Unlike "Sir", Pan is used both ways between persons of both equal and unequal rank (a waiter will address a guest as "Pan", and the customer reciprocates, much like using "Monsieur" in French). Using "Pan" with only the first name is regarded as a disrespectful way of addressing people, even somewhat condescending, when it is used to a superior. Using Pan with only the surname, however, is normally respectful if talking about somebody. "Pan" is never used about oneself (unlike "Mr").
"Pan" is also used as a kind of personal pronoun in a similar way as "Usted" in Spanish or "Lei" in Italian (unlike French 'Monsieur' or German 'Herr', which require the use of 'vous' and 'Sie' respectively). A non-Slavic language, Lithuanian, has a similar title, "Ponas".
Other titles.
"Spadar" appears in Belarusian. It is a simplified version of "Haspadar", which is related to "Gospodin" or the Slovene "Gospodar". "Gaspadorius" and "gaspadinė" for a woman appears in Lithuanian language. It is an archaic word and it is not used today in the general language, however it is not extinct and sometimes used in a countryside. It originated from Proto-Slavic, ultimately from *gospodь, compare Bulgarian, Serbo-Croatian and Ukrainian господар (hospodar), which means householder, master of the house or head of a household.
"Vladyka" (literally, ruler/master), is used when referring to a bishop or patriarch in Eastern Orthodox churches.
"Sudar", appearing without a personal name, was formerly used in Russian. It may be connected to the Russian title of a head of state, "Gosudar". Its Ukrainian counterpart was "(Pane) Dobrodiyu" or "(Pani) Dobrodiyko" (pl. Dobrodiyi). Those titles became obsolete and are now found only in novels. Appeal of "Shanovni Dobrodiyi" ("Dear Goodwill") is still used solemnly to many people.
In Ukrainian, "Panych" was once used to refer to noble youngsters and generally referred to the Polish people. It is spelled "Panicz" in Polish. 
Under communism.
The equivalent of "Comrade" replaced most titles in the Communist-era Eastern bloc, except Poland.
In Poland, "Obywatel" ("citizen") replaced "Pan", which was restored after the fall of Communism. The word "citizen" was chosen for ideological reasons as "pan" (sir) was historically a title of a nobleman. The equivalent of Russian comrade – "towarzysz" – was a title reserved only for communist party members.